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SMITHSONIAN IN ee Ws SAIYVYSIT LIBRARIES SA1uVUdIT_ LIBRARIES INSTITUTION INSTITUTION INSTITUTION AN 2 Fs S A ILIWS JNIAN {LIS avs¥M SGV INIAN 3 fil fe : i hs A} aan De ESSA _ ' fi ay HANDBOOK OF ZOOLOGY. : c ‘ ? {? A . (iho). Gly ‘gt a at 1 OX * “FDO Fike oo 2 ae / f fhe ne — ate YALL . HE ie oh — j os Qe HANDBOOK OF LOOLOGY BY J. VAN DER HOEVEN, PHIL. NAT. ET M.D. PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF LEYDEN, KNIGHT OF THE ORDER OF THE DUTCH LION AND OF THE SWEDISH ORDER OF THE POLAR STAR, MEMBER OF THE ROYAL ACADEMY OF SCIENCES, OF THE DUTCH SOCIETY OF SCIENCES AT HAARLEM, OF THE IMPERIAL LEOPOLDO-CAROLINE ACADEMY, OF THE IMPERIAL SOCIETY OF NATURALISTS AT MOSCOW, COR- RESPONDING MEMBER OF THE BRITISH ASSOCIATION, OF THE ROYAL ACADEMY OF SCIENCES AT TURIN, OF THE IMPERIAL ACADEMY OF MEDICINE AT PARIS, ETC. a Trado que potui. IN TWO VOLUMES. VOLUME THE SECOND. (VERTEBRATE ANIMALS. ) TRANSLATED FROM THE SECOND DUTCH EDITION BY THE REV. WILLIAM CLARK, M.D. F.R.S. &c. LATE FELLOW OF TRINITY COLLEGE, AND PROFESSOR OF ANATOMY IN THE UNIVERSITY OF CAMBRIDGE. Cambridac: PRINTED AT THE UNIVERSITY PRESS, FOR LONGMAN, BROWN, GREEN, LONGMANS, AND ROBERTS, LONDON. 1858. ie aos i i oa 94 CR a ~~ >, ae ee « 1 ne tatak eon ae foyer wy airy Te etta® . VVIQNA PPP. BRD Te Oe Mod Bh? ews OK H Kan " 4 ay en OAS! = es Y STEJNEGER COLLECTION National tv ev ———— —.-—— TO RICHARD OWEN, Esqr. F.R.S. &e. &e. Se My pear Sir, I beg leave to offer you a joint tribute. The author of this work expresses much satisfaction that the translation of it is dedicated to one whom he so greatly respects and admires. To myself it affords peculiar pleasure to present to you, in an English dress, The Hanpspook oF Zoonoay of one so learned, which, ap- pealing in so many of its pages to the authority of your works, recalls those epochs of still increasing lustre in that distinguished career which is the admiration of the cultivators of that and the allied branches of natural science throughout the world. That you may long enjoy in health and happiness your well-won laurels is the sincere wish of your friend and admirer THE TRANSLATOR. CAMBRIDGE, Feb. to, 1858, ES adenine. “a win Yas ma tensd9h2 aun “ae Ae ehaics aif} _ Ws tes Aci: tun *. mii . the i ity th ~ XXXIX. A XT, Order IX. Chiroptera Fam. XLI. A XLII. Order X. Ptenopleura . Fam. XLII. Order XI. Quadrumana . Fam. XLIV. 6c XLY. Order XII. Bimana Fam. XLVI. CONTENTS, Tylopoda Hlaphii Cavicornia Efodientia Tardigrada . Duplicidentata Subungulata Aculeata Palmipedia Murina Cunicularia Muriformia . Eriomyina Dipoda Sciurina Pinnipedia Felina . Viverrina . Canina . Mustelina . Ursina . Talpina Soricina Erinaceina . Nycterina Pterotocyna Galeopithect . Lemurina Simice Erecta . PAGE . 643—660 . 644—646 . 646—649 649-—660 . 660—665 - 660—664 . 664—665 665 —696 . 666—667 . 667—669 . 669—671 . 671—672 . 672—680 . 680—684 . 684—688 . 688—689 . 689—691 691—696 . 696—730 696—7o2 » 703—795 705—710 . 710—712 712—1718 . 718—721 721—724 + 724—729 729—730 » 731—742 732—740 » 740—742 742—743 » 742—743 - 743—756 * 743—747 - 747—756 757—758 - 757—758 ae ret) Mk tiny ERRATA AND CORRECTIONS. Additional in Vol, I. Page Line 283 20 from top, for antenne read muscles. 317 5 from bottom, for Condylura read Cordylura. 347 14 from top, for under jaws read upper. 385 before 1. 26, Family xxzil. insert: B. Phytophaga. Abdomen sessile. Larva furnished with six or numerous feet (to correspond to section a. Hntomophaga, \). 371). 556 note, l. 15, 17, for HANN read Haun. 604 1 for Parabea read Porcellio. 769 5 from bottom, for probable read improbable. In Viol) TE. 17 after last line of note 2, add Berolini, 1847, 4to. 26 7 from bottom, for Geschied.er read Geschieden. 37 21 for Sphyrna read Sphyra. 53 14 from bottom, for Ammodotes read Ammodyies. 62 16 from bottom, for aguila read aquila. 63 5 insert: +t No spur at the base of tail (compare p. 62, 1. 7). 7r 15 from top, for 76—78 read 69—78. 72 1 for Kizrary read Kirrary. 73 3 note, for Prieslebenense read Preislebenense. AA 4 note, for Prieslebent read Freislebent. 78 7 from bottom, for RANZINI read RANZANI. 3 7 -_ 82 and g from bottom, for Panserwelse read Panzervelse. 84 17 for five rays read three. 92 g from bottom, for AGARS read AGAss. 135 1 for Xyrichthys read Xirichthys. 262 7 from bottom, for Merrem read MERREM. 266 17 from bottom, for Opisthoglyptes read Opisthoglyphes. 319 «617_~=«éfrom bottom, Cistuda: is not this a misprint in FLEMMING’S work for Cistula? 555 1 for Philodota read Pholidota. 615 12 and 5 from bottom, for Dendrologus read Dendrolagus. - oe 7 a a —_ SS "y = ie no aad be rors veet0 0 7 . a oe Sovcaile hy Mmoadpy% La J i} ow, Sfieaiat a9 be . : ot oe | ; hon vi sath Ye $0) A Piteseyes 4) i® ns iahiahanihr eye alt eavns WE et ier ‘eal her nde ot B Meagl RE he ebb ae SS coms ri a 7, eft i av jectstingn Gen Rit J ee (hy s. | pa 4 CN el oe aed soe :elaanieny oneal te, planus va tbe bs she adhe : br iy na vyilere datas doclt-ties Marl vib ean Sy aie . Zina fbi Aitiia > Arey toured’ DT hd no 8 asi ® at a” 38 al? et cae yt? et aR Wh ae aif i of _-* — Pai al @ -i +) 4; “Bhi s t. are TT in ti sits SJ448 One ON THE LAST FOUR CLASSES OF THE ANIMAL KINGDOM IN GENERAL. We have already seen (Vol. 1. p. 32) that modern Zoologists, in imitation of LAmARcK and Cuvier, unite the Fishes, Reptiles, Birds and Mammals, under the common name of vertebrate ani- mals, to form a large division of the animal kingdom. In these animals the main trunk of the nervous system, the spinal cord and the brain, is inclosed in a bony or cartilaginous cavity, which is usually formed of distinct rings or vertebra. The muscles are sdtiohiy all inserted into internal supports, which, together with the hard investiture of the brain and spinal cord, ee what is called the frame-work or skeleton. The body has in general a symmetrical form on the two sides, and is divided by an imaginary axis into a right and left half, in which especially the organs of animal life, the nerves and muscles, are correspond- ingly formed and placed. There are never more than four limbs present in these animals; some have only one pair of limbs; in others the limbs are entirely absent. Their blood is red}. The sexes are always distinct, so that bisexual individuals occur as pathological exceptions alone. There are always two jaws, one situated above the other, of which the lower especially is moveable. The motion of these parts occurs vertically and not laterally, as is the case in the Articu- late Animals. Ordinarily the jaws are armed with teeth; in the 1 In Aimphioxus lanceolatus alone has colourless blood been observed; J. MUELLER Veber der Bau u. die Lebenserscheinungen des Branchiostoma lubricum Costa, Amphioxus lanceolatus YARRELL, Berlin, 1844 (Physik. Abhandi. der Akad. d. Wiss. zu Berlin, .Jahrgang, 1842). VOL. II. 1 2 ON VERTEBRATE ANIMALS tortoises and birds a horny covering, and in the whales a row of horny plates (in the upper jaw,—the so-called baleen), takes the place of the teeth which are wanting. Teeth are, as it were, ossified papille on the mucous membrane of the jaws; they may also occur on the palate, on the tongue, and, in fishes, on the branchial arches. The intestinal canal is of various width in different parts, and receives various fluids, which are secreted by different glands. Such a fluid is the saliva, which is mixed with the food during mastication and deglutition, such also the bile and the pancreatic juice. In all vertebrate animals the liver, besides arterial blood, receives also much venous blood, which, as it returns from the viscera, is taken up by a venous trunk (the portal-vein), that like an artery divides into branches to be distributed through the liver. From the food which has been changed by the action of the stomach and of these secreted fluids, and is called chyme, the chyliferous or lacteal vessels take up the nutritious part, and convey it in a fluid state (called chyle) to the veins. Other vessels, in addition, which resemble the lacteals, but which are not, like these, spread over the intestinal canal, absorb from the different parts of nearly the entire body a watery fluid (lymph), which becomes mixed with the chyle. These vessels, with the preceding, make up the lymphatic system, which appears proper to vertebrate animals alone. They begin with blind extremities, and are formed of an epithelium, which is covered by a fibrous membrane formed of fila- ments running longitudinally and mutually crossing in form of a net. On the outside of this membrane lies a covering of circular fibres which pass into those of the surrounding connective tissue. In the interior of the lymph-vessels, at least in most, are placed in mammals and birds membranous valves, which favour the motion of the fluid from the circumference of the body inwards, towards the larger vessels. In mammals and in man almost the whole fluid of this entire system meets in a principal stem, the thoracic duct, which opens into the left subclavian vein. There are, how- ever, smaller trunks also, which are situated on the right side, and sometimes form connexions with other veins. The lymphatics form repeated networks, and also as in warm-blooded animals, by their rolling up and intertwining, glands improperly so named (glandule conglobate). The spleen is also a part which is found in vertebrate animals alone, and of which the presence and the IN GENERAL. 3 function are probably in connexion with those of the lymphatics’. This organ is situated in the neighbourhood of the stomach, and thus more on the left side, at the upper part of the abdominal cavity; it consists of a red, highly vascular tissue surrounded by a fibrous external membrane, from which white productions as envelops of the blood-vessels penetrate the internal soft substance and support it like transverse joists. Peculiar vesicles, of microscopic size, filled with a white pultaceous mass (Malpighian bodies), are attached to these productions; the red pulpy substance contains many red- brown granules’. We have already indicated that the blood of vertebrate animals is red; hence the ancients, though incorrectly, ascribed blood to these animals alone, and called the invertebrates bloodless animals. The veins of the body convey the blood to the heart, from which it is driven to the respiratory organs: that is, the heart of vertebrate animals is venous. In invertebrate animals, on the contrary, the heart is arterial, i. e. it receives those veins which return the blood from the respiratory organs, and sends the blood to the vessels which are distributed to the various parts of the body. In verte- brate animals, an arterial heart also may be present, but never unless at the same time a venous heart be found. The two hearts in that case lie close together (the two ventricles in mammals and birds), or they coalesce to form one cavity, as in most of the reptiles. ‘Thus, whenever the heart receives the veins of the body alone, as in fishes, then there is only one auricle and one veniricle; if, on the other hand, it receives the veins of the body (the vene cave), and the veins of the respiratory organs as well, then there are two auricles (atria), but not on that account always two ven- tricles. In those vertebrate animals in which the two ventricles are united to form one cavity, not all the blood but only a part of 1 It is asserted that the chyle acquires greater coagulability by admixture of fluid contained in the lymphatics of the spleen, Compare P. W. Lunp Physiologische Resultate der Vivisectionen neuerer Zeit. Kopenhagen, 1825, 8vo, s. 78—83. * The spleen appears to be absent in the Cyclostomes alone, although a gland situated on each side of the superior orifice of the stomach is referred to it by MEYER and others. Notwithstanding, however, the general presence of the organ in verte- brate animals, it does not seem to be essential to life, but may be excised without danger, as has occurred as well in animals as in man; see the notes in HALLER Le- ment. Physiol. Vi. p. 421. : ) ee 4 ON VERTEBRATE ANIMALS it, is conducted to the respiratory organs; arterial blood is mixed with venous blood. The respiratory organs of vertebrate animals are gills or lungs. Vertebrates alone inspire by the mouth, and such as have lungs exspire by the mouth also. In all vertebrate animals kidneys are present, parts by which the urine so rich in nitrogen is secreted, and of which the internal structure consists of fine tubules. In the lower vertebrates these tubules unite to form branches which open into excretory ducts (wreteres) running along the whole kidney; in birds and mammals they unite to form bundles—pyramids,—which are arranged around the cup-like commencement of the ureters. The two ureters, again, often terminate in a bladder in which the secreted fluid is collected before being discharged. As to the sexual organs, we have already stated above, that the sexes are constantly distinct. Not by any means, on that account, however, is there a copulation in all, but sometimes the eggs, as in most fishes, are impregnated after they have been laid. The ovary is single or double (paired). In this organ the eggs are formed, and leave it in order to undergo further development in another situation. With most vertebrate animals this situation is external to the body of the mother, and the development depends upon external conditions of light, water and warmth: according to the difference of these conditions the egg may require a longer or shorter period for the development of the germ; the germ alone of a future independent being is present at the time of birth, or of the separation of the egg from the body of the parent animal. In other cases the eggs, so to speak, are brooded within the parent body itself; and here the birth, which terminates the period of foetal life, is contemporaneous with the relinquishment of the foetal enve- lops. Such animals are usually named viviparous’, but the limit between these and the oviparous cannot always be defined with precision. Most fishes and reptiles and all birds are oviparous. In the yolk of eggs, that still lie in the ovary, there is seen a small transparent vesicle or a cell, which is surrounded by a ring or by a small accumulation of a granular mass. This germ-vesicle, 1 BuRDACH names these animals nudipara, Die Physiologie als Erfahrungswissen- schaft, 1. Leipzig, 1828, s. 45 (2te Auflage, 1837, s. 48). IN GENERAL. 5 first accurately indicated by PuRKINJE in the bird’s egg, also con- tains a nucleus, to which the name of germ-spot (macula germinativa) has been given, and of which the discovery is due to R. WAGNER. The investigations of the latest period have demonstrated the uni- versality of these parts of the ovarian egg. When the egg passes from the ovary into the oviduct, the germ-vesicle disappears, and is replaced by a disciform germ-membrane from which the first development of the embryo takes a beginning. In mammals, as early as the latter end of the seventeenth century, the vesicles of the ovaries had become known through the investigations of Rrc- NERUS DE GRraar, which after their discoverer were named follicult graafiant, and were generally regarded as eggs. But only about twenty years have passed since Von Barr found the true egg in the ovary of mammals, which, however, he took for the germ-vesicle then lately discovered by PuRKINJE, and thought that in mammals alone this vesicle passes from the ovary into the oviduct, whilst in oviparous animals the entire egg, the yolk, is taken up by the oviduct. Consequently, according to Von Barr, the folliculé graa- fiant were to be regarded as ovarian eggs, which inclosed within them the ovwm fetale, the germ-vesicle’. It was afterwards? dis-’ covered that this so-named ovwm fetale also included within ita germ-vesicle; in other words, that it was a perfect egg, which was still further confirmed by the discovery of the germ-spot in this vesicle. The folliculi graafiant are thus not eggs, but each of them contains an egg which occupies only a small space of it, but yet in its composition, in its inclosing a germ-vesicle with its germ-spot, is similar in form to the egg in the ovary of birds and other animals. On development the germ lies, as in invertebrate animals, in form of a gelatinous disc on the yolk, immediately under the vitelline membrane. ‘The germ-disc separates into three layers; a serous layer the most external, a mucous layer the most internal, and a vascular layer between the two, but more intimately connected with the mucous layer. In the middle part of the serous layer arise the vertebral column, the spinal marrow and the cerebral mass. On the outer surface of the serous layer arise two projecting lines, which iC. E. A. De Barer De Ovi Mammalium et Hominis genesi. Lipsi, 1827. 2 Costa, WHARTON JONES, VALENTIN, BERNHARDT enz. 6 ON VERTEBRATE ANIMALS afterwards unite above and enclose the spinal marrow. Beneath, this layer bends itself round in order to form the abdominal cavity. The mucous layer gives origin to the intestinal canal. It is worthy of remark that the position of the embryo with respect to the yolk differs from that in the articulate and other invertebrate animals. In these the yolk lies on the dorsal surface, in the vertebrate animals always on the abdominal surface of the embryo. ‘The central portion of the germ, from which the develop- ment begins, is, in vertebrate animals, the dorsal part. Hence it arises also, that if we suppose the intestine to be the axis by which the body is divided longitudinally, the principal mass of the nervous system, the stem—the brain and spinal marrow—lies above this axis, whilst the gangliated cord of articulate animals which corre- sponds to the spinal marrow lies under its axis, on the abdominal surface; the spinal marrow is here replaced by an abdominal cord. Inversely the heart in vertebrate animals lies below, in invertebrate animals above the same axis’, We have seen above that the dorsal vessel of insects takes in them the place of a heart (compare Vol. 1. p. 258). The position of the central part of the nervous system (the spinal cord and brain) on the dorsal surface, and its enclosure in a special cavity distinct from that of the viscera, form two principal characters of vertebrate animals. If we follow the branches from which the nerves of the skin or those of the muscles arise to their origin in larger and still larger trunks, then we find that they all run towards the brain or the spinal marrow, and lose themselves in the substance of these parts. Brain and spinal marrow are consequently the central parts of the nervous system of animal life. They are, however, only two divisions of one and the same whole, of which the development and magnitude are usually inversely proportional to each other. In the most perfect vertebrate animals, namely the mammals and especially in man, the mass of the brain far surpasses that of the spinal cord. In the brain and in the spinal cord the nerve-substance appears under two modifications. Chemical investigation has 1 Compare H. RatHKe Untersuchungen iiber die Bildung und Entwickelung des Flusskrebses. Leipzig, 1829, s. 77—90; see also Barr De Ovi Mammal. et Hominis genesi, p. 24. IN GENERAL. 7 hitherto indicated no remarkable difference between them; only the one seems to contain less fat, a softer albumen’, and more water. This is of a grey colour and receives a greater quantity of blood- vessels than the other, which is white and is named medullary sub- stance (comp. Vol. 1. p. 11). This denomination and that of corti- cal substance are derived from the relative position of the two substances in the brain, where usually the white substance is sur- rounded by the grey. In the whole of the spinal marrow on the contrary the cortical substance is situated internally. In vertebrate animals two nervous systems may generally be distinguished, one for the vegetative, another for the animal life, although many invertebrate animals also, as we have formerly noticed, already indicate a commencement of this division®. On the other hand, in some vertebrate animals the nervus sympathicus is little developed, and is in part replaced by the vagus. The nerves of vegetative life unite in irregular flat or round bodies which are named nerve-ganglia. Here the branches of nerves form many nets or plexuses, which principally surround the blood- vessels. The whole is destitute of symmetry. In proportion to the larger development of the nervous system, the organs of the senses in vertebrate animals are also more perfect. Four of these, the organs of sight, hearing, smell and taste, are situated in the anterior part of the head, included in bony cavities and protected. The olfactory organ, formed by a folded mucous membrane upon which the branches of the first-pair of nerves are spread out, is in most fishes entirely segregated and placed on the upper surface of the bony head, but in those vertebrates that breathe by lungs is connected behind with the cavity of the mouth, and so with the respiratory organs. The sense of feeling (and more particulary that of tact) is in some animals especially developed in the fingers, in others in the lips, in others again probably in the tongue. Eyes are always present, as it would seem, in vertebrate animals, although they are often very small and sometimes concealed under the skin, and in certain fishes are two little balls surrounded by pigment without refracting media, and so can have no other office than that of distinguishing light. 1 Joun Chemische Tabellen des Thierreichs, s. 7. 2 See Vol. 1. p. 766. 8 ON VERTEBRATE ANIMALS An especial characteristic of vertebrate animals consists in the possession of an internal skeleton, of which the spinal column forms the stem. However strange it may sound, it is nevertheless true that all vertebrate animals do not possess vertebre. The first com- mencement of the skeleton is a cord situated in the back, which is sometimes fibrous but usually gelatinous, and consists of elongated cells, and is inclosed invariably by a fibrous sheath. This cord (chorda dorsalis) does not undergo ossification, but during the formation of the bony vertebre is gradually superseded or included by the ossified sheath. At the same time there are imperfect fishes where this dorsal cord is persistent, and where no special vertebrae are found. The spmal marrow lies above this cord, protected by two fibrous lamine, or by cartilaginous arches. Consequently a vertebral column cannot be assigned as the universally prevalent type of vertebrate animals, but first of all a dorsal cord (chorda dorsalis) which either persists during the whole of life, or is replaced by a vertebral column; and next, a spinal marrow, as central mass of the nervous system, which is situated upon this cord or upon the vertebral column. The basal pieces of the cranial bones, upon which the mass of the brain rests, resemble the bodies of vertebrae. The brain is sur- rounded by very wide vertebral arches’. All the cranial bones however do not arise from ossification of the original cartilage which is to be regarded as a continuation of the vertebral column in the head. This cartilage, this primordial skull, is in part covered over and inclosed by bones which arise from a membranous dblastema which hes upon the cartilage, and so have never been cartilaginous’. In general all fibrous and tendinous parts may become bony. Hence the muscles of the legs im birds are seen to terminate in bony ten- dons ; in other animals portions of bone are found in the diaphragm, 1 OKEN adopts three cranial vertebre: Ueber die Bedeutung der Schidelknochen. Jena, 1807, 4t0; OweEn four: On the archetype and homologies of the Vertebrate Skeleton. London, 1848. ? Attention was directed to this point by the celebrated physiological anatomist L. JACOBSON especially, See his memoir Om Primordial-craniet in Férhandlingar vid de Skandinaviske Naturforskarnes tredje Mote. Stockholm, 1842, pp. 739—744; compare also A. KOELLIKER in Berichte von der Kéniglichen Zootomischen Anstalt zw Wiirzburg (Leipzig, 1849), s. 35—42, where also are found anatomical notices on the labours of some writers who preceded JACOBSON on this point. IN GENERAL. 9 in the crocodiles abdominal ribs, which are nothing else than the ossified transverse tendinous strips of the straight muscles of the abdomen. The vertebral column and the skull are the only essential parts of the internal skeleton. The limbs are wanting in most snakes and in some fishes, the ribs in the frogs and others. If now from the skeleton of a four-footed mammal or of man the limbs and the ribs be subtracted, then there will remain nothing but the verte- bral column and the bony head. The division of vertebrate animals into four classes, derived from Linnaus, has since his time been generally adopted and maintained, although some writers have wished to compose a fifth class from the scaleless Amphibia. ‘That division is founded upon the temperature of the blood! and of the internal organs, upon the various forms of the heart, upon the difference of the respiratory organs, which are either gills or lungs, and upon the distinction of the parturition, the laying of eggs or the bringing forth of living young. . These four classes are those of fishes, reptiles, birds and mam- mals. Fishes and reptiles are cold-blooded, birds and mammals warm-blooded. Fishes breathe by gills, the remaining vertebrate animals by lungs; birds and mammals are thus warm-blooded ani- mals that breathe by lungs; but of these the first are oviparous, the last viviparous. 1 Tf, during life, the temperature of animals undergoes only very little variation, and is almost entirely independent of that of the medium in which they live, then they are said to be warm-blooded. Animals whose temperature is dependent in great part on that of the air or of the water, in which they reside, are, on the other hand, named cold-blooded. CLASS XIV. FISHES (PISCHS)'. THE Fishes are vertebrate cold-blooded animals, which live in water, and breathe by gills. Their external form is very various, yet in their internal structure there is still a correspondence suf- ficient for regarding the class of fishes as a natural division of the animal kingdom. Linnaus and Brisson, at the beginning of the preceding century, separated from it the cetaceous animals, which, in the first edition of the Systema Nature, the great Swedish Naturalist had arranged with the fishes, although ArISTOTELES had already regarded the fishes and cetaceans as two large distinct genera or classes, adducing the gills as a special characteristic of fishes, which, moreover, as he sagaciously remarked, differ by the 1 On the class of fishes may be consulted amongst other works: P. Beronut De Aquatilibus Libri uu. Parisiis, 1553 (forma oblonga). H. Sarvianti Aquatilium Animalium Historia. Rome, 1553, folio. G. RonpEterit De Piscibus marinis. Lugduni, 1554, folio. G. WiLLUGBEII Historia Pisctum, cura J. Rast et C. Mortimeri. Londini, 1743, folio. P. ArteDt Ichthyologia, s. opera omnia de Piscibus posthuma, edidit C, LINNZUS. L. B. 5738, 8vo. M. E. Buoca @konomische Naturgeschichte der Fische Deutschlands. Berlin, 1782, 1784, 111. Bd. 4to (with col. plates in folio). M. E. Buocn Ichthyologie ou Histoire naturelle générale e particuliére des Poissons. Berlin, 1787—1797, x11. Vol. fol. (with 432 coloured plates). Biocu Systema Ichthyologie, edidit J. G. ScHNEIDER, 1801, 8vo, 1 Vol. (with 110, mostly coloured, plates). LacerEpE Hist, naturelle des Poissons. Paris, 1798 to 1803, 4to, v. Vol. (also in small 8yo, XI. parts, with many figures). CUVIER and VALENCIENNES Histoire naturelle des Poissons. Paris, 1828—1849, 22 Vols. (8vo or 4to) with 650 plates, coloured or uncoloured. The whole contains the Acanthopterygit and Malacopterygii abdominales. VALENCIENNES has undertaken a second series on the remaining Malacopterygit and the Chondropterygit. On the anatomy of fishes, besides the work last cited, in which the internal structure of this class is illustrated by many figures from the river Perch, compare: A. Monro The Structure and Physiology of Fishes explained and compared with those of Man and other Animals. Edinburgh, 1785, fol. R. Owen Lectures on the Comparative Anatomy and Physiology of the Vertebrate Animals. Part 1. Fishes. London, 1846, 8vo. Special works on the fishes of particular countries and writings on different points of the anatomy of these animals will be cited now and then in the sequel. - FISHES. 11 absence of the glands that secrete milk, from the sucking dolphins and cetaceans. LINN#£US, in the last edition of his arrangement, referred the cartilaginous and some other fishes, to which he erro- neously ascribed, in addition to gills, lungs also, to the class of the Amphibia. This position was rejected by subsequent writers, and GMELIN, in the thirteenth edition of the Systema Nature, restored these animals to the fishes. Fishes, as is well known, occur in water alone; and, however some or even many species from all the other classes of animals live in water, still fishes form the greatest number of the in- habitants of water, at least among vertebrate animals; so that it is not strange that, by the uninitiated and in common language, the appellation of fishes should be transferred to other water-animals. Let us first consider shortly the external structure of fishes; this will afford us, at the same time, the opportunity of explaining some terms which are employed in the description of these animals. The body of fishes may be divided into head, trunk, and tail. The head is an immediate continuation of the trunk; fishes have no proper neck, since the respiratory organs are seated under the head, and the thoracic cavity immediately succeeds to that of the mouth, or is even confluent with it. Hence the form of the body is very simple, usually attenuated gradually towards the two extremities. In some the hinder end is, as it were, cut off, as in the sun-fish (Orthagoriscus). In the rays the tail is much narrower than the trunk. The body of most fishes is compressed laterally (corpus com- pressum 8. cathetoplateum), so that the section is an oval, of which the back forms the broadest end. In others, as in the rays, it is depressed or flat (corpus depressum s. plagioplateum); in others, still, it is cylindrical, as in the eels; in others almost spherical, as in some species of the genus Diodon ; in some, finally, angular, sur- rounded by flat or slightly concave surfaces, meeting in three or four projecting edges, as in the so-named Coffer-fishes, the genus Ostracion. In general, the body is covered with scales (corpus sgwamosum). Sometimes the scales are small, and the smooth slimy skin seems to be naked, as in the eels; in some fishes, however, as in the cyclostomes, the scales are really wanting (corpus nudum s. alepi- dotum). 12 CLASS XIV. On each side of the body lies a row of apertures, sometimes extremities of bony tubes or of small pipes perforating the scales, and forms the so-called lateral line (linea lateralis); under this lateral line a glandular tissue, at least when these parts are more developed, has been observed. The slimy fluid, with which the body of fishes is covered, is secreted here. The line hes, im some cases, closer to the back, in others, more towards the abdominal side; it is in some fishes (as Chromis, Xirichthys) interrupted, 1. e. behind it ceases on the back, and suddenly arises lower down, pursuing a new direction on the tail. The head of fishes may, like the body, be narrow and compressed, or flat and broad, naked or scaly. In the frog-fish (Lophius pisca- torvus) it is almost as large as the body, in most fishes much smaller. The jaws are not always equally long. In some, as in Xiphias, the upper jaw, in others (especially in the genus Hemidramphus) the under jaw is extraordinarily elongated. The aperture of the mouth in the sharks, rays and sturgeons is situated on the under side, in most fishes at the anterior ex- tremity of, the head. In the genus Uranoscopus the mouth is placed upwards. ‘The lips and the jaws have often various appendages, filiform feelers (tentacula, cirri), Kc. The teeth are distinguished by their form and the different parts on which they are affixed. Besides the jaws, they may occur on the vomer, on the palate, the tongue, the branchial arches, and the small bones of the gullet. The nasal apertures and the eyes are the only organs of sense that can be distinguished externally. In the genus of the soles (Pleuronectes) the two eyes are placed on the same side of the head. In others they lie one on each side, sometimes turned more towards the upper surface (as in Uranoscopus), rarely more downwards, as in the sucking-fish (Heheneis). The gills have ordinarily on each side behind the head a single opening, through which the water, on expiration, is expelled (aper- tura branchiarum), and which mostly is in form of a semilunar fissure, convex backwards. ‘They are protected by bony plates as a cover (operculum), of which the posterior margin is free. Beneath this is a membrane, which is folded and supported by bony rays that can expand it (membrana branchiostega). We shall advert to these parts more particularly in the sequel. FISHES. 13 The fins are in part unpaired, situated in the plane that divides the body into two lateral halves, in part paired, lying on each side. The last may be four in number: two pectoral fins (pinne pec- torales), which are placed higher and behind the gills, and two ventral fins (yinne ventrales), which are situated more below. In some fishes, as the haddock, these last are placed quite forward, in -front of the pectoral fins (pisces yugulares); in others they lie almost directly below the pectoral fins (pisces thoracic?); but usually they lie nearer to the tail, behind the pectoral fins, as in the carp (pisces abdominales). The unpaired fin at the end of the tail is called the caudal fin (pinna caudalis), that which is attached to the body below, the anal fin (pinna analis), that which is situated above upon the back, the dorsal fin (pinna dorsalis).: The dorsal and the caudal are sometimes divided, or several separate fins are placed behind each other. Adipose fin (pinna adiposa) is the name given to a small dorsal fin without rays, which lies behind the ordinary dorsal fin, as in the salmon. The small bones which support the fins, and between which the skin of the fins is extended, are named rays (radii). These are either composed of joints and often split at the point into different filaments (radii molles), or simple, hard and pointed (aculed s. radii spinost). When these last are present, they are situated at the fore part of the dorsal and anal fin. The number of rays is used as a specific character. Ordinarily the ventral fins are situated in front of the anus, whilst the anal fin begins behind it. In some fishes that have no ventral fins, the anus is placed far forward, close under the head (the genus Sternarchus). This may suffice for the external form of fishes. We must now consider their internal structure a little more closely, and to that end shall first treat of their frame-work?. 1 On the osteology of fishes, besides the general works on comparative anatomy by Cuvier, Mecken, &c., the following may be consulted: Bosanus Versuch einer Deutung der Knochen im Kopfe der Fische in OKEN’S Jsis, 1818, I. 8s. 498—510; GEOFFROY Sarnt-HinarrE Philosophie Anatomique, 1. Paris, 1818, 8vo; G. BAKKER Osteographia piscium. Groninge, 1822, 8vo (with folio plates, in which the parts of the skeleton are principally illustrated in the haddock); L. Agassiz Recherches sur les Poissons fossiles. Neuchatel, 1833—1843, 4t0, I. pp. 9I—152 (dw Squelette des Poissons en general); also in the work itself many osteological observations and descriptions of the skeleton of different genera are to be found, ex. gr. of Zsow in the fifth part, 14 CLASS XIV. The chief constituents of bony tissue are, as is well known, phosphate of lime and gelatine. The organic constituent of the cartilaginous bones in sharks is, according to CHEVREUL, a peculiar animal matter, which, in its chemical properties, has more resem- blance to mucus than to gelatine. According to MUELLER, the gela- tine from the bones of osseous fishes does not jelly. The cartilagi- nous fishes have some parts of their skeleton which are more ossified, and contain much phosphate of lime, as the bodies of the vertebre of sharks and rays, or they are coated with a hard ossified layer}. The difference therefore between cartilaginous and bony fishes is not very definite, since in these last moreover there is much cartilage remaining, especially in the skull. We will now, first of all, confine ourselves to the form of the skeleton. It consists of the trunk, the head, the bony or cartilagi- nous apparatus of the respiratory organs and the fins. The spinal column consists of dorsal and caudal vertebre; for, since fishes have no pelvis, there are no sacral nor lumbar vertebre; as little are there cervical vertebra, for the cavity of the thorax is situated under the head. Some writers indeed name those vertebre that lie nearest to the head and to which no ribs are attached, cervical ver- tebree; but since there are many fishes that have no ribs at all, no general use can be made of this distinction. The notochord [Owen] (chorda dorsalis) is persistent in some imperfectly organised fishes, and supplies the office of distinct bodies of vertebrae. It is deserving of remark that this embryonal state was very general in fishes of the earliest geological period, whence the explanation is given that, in the remains of the so-named Ganoids no bodies of vertebree are met with’. In most of the cartilaginous fishes, however, and in the bony fishes, bodies of pp. 60-—68 ; OWEN Lectures on the Comp, Anat. and Physiol. of the Vertebr. Anim. Pt. 1. Fishes. London, 1846, pp. 40—162. Here his theory of the cranial vertebre is also fully propounded. The richest collection of figures of the piscine skeleton is to be found in F, RosEn- THAL’S Ichthyotomische Tafeln. vi. Hefte. Berlin, 1812—1825. CuviER, in the first part of his Hist. natur. des Poissons, has figured and described the skeleton of Perca fluviatilis in detail. 1 Abhandlungen der physikalisch-mathematischen klasse der Kénigl. Akademie der Wissensch. zu Berlin. 1834, s. 136. * AGASSIZ ascribed this previously to the accidental decomposition. Recherches sur les Poissons fossiles, 11. 1, pp. 83, 84. FISHES. Bi vertebrae more or less ossified are present. These present in front and behind a conical cavity which is filled with a soft matter, the remains of the gelatinous cord. These two cavities often communi- cate in the middle of the body of the vertebrae by a small aperture between them, and thus have the form of an hour-glass placed horizontally. In Lepidosteus the remarkable exception occurs, that the bodies of the vertebre exhibit a hemispherical surface at their anterior part, an articular head, and at the back part are con- cave’. Above the body of the vertebre is situated a process on each side (newrapophysis OWEN). These processes are ossified earlier and more generally than the bodies of the vertebre ; they approach each other above, and thus form a ring above each of the vertebre, the superior vertebral arch, in which the spinal marrow is lodged, and on which a spinous process is usually affixed. At the base of this superior vertebral arch there is generally situated forwards and backwards, sometimes forwards alone, a small articular process on each side, which serves, with the conical cavities of the bodies of the vertebra, to connect the vertebra ; the anterior articular process overlaps the posterior process of the preceding vertebra, and is received in an excisure at the base of the superior vertebral arch. Sometimes, as in Polypterus, the superior arches of the bodies of the vertebre remain distinct, but in most fishes they sooner or later coalesce with them. The dorsal vertebra have transverse processes (parapophyses OWEN); the caudal vertebre processes which bend downwards and approach each other to form in this way an inferior vertebral arch, within which the trunks of the blood-vessels are situated that run beneath the bodies of the caudal vertebra. The number of vertebra is very different in different fishes ; in Orthagoriscus mola, for instance, there are only seven- teen, in Anarrhichas lupus seventy-six, in Murena more than an hundred. The tail is formed by nearly the half, and often by many more than the half, of these vertebree. For the tail is in fishes the chief instrument of motion, and in most of them constitutes the greatest part of the body; all the organs are pushed forward to leave room behind for the large muscular mass which serves for motion. 1 Agassiz Rech. sur les Poiss. fossiles, 11. 2, p. 23, Tab. f', figs. r1o—12. A similar disposition is found in most of the Reptilia, but in them the articular head is behind. 16 CLASS XIV. In most fishes ribs (plewrapophyses OWEN) are present: each rib is attached to one vertebra alone, sometimes to its body, but ordinarily to the extremity of the transverse process. These ribs do not inclose the thoracic but the ventral cavity, and are not at- tached to a sternum below. Only in very few fishes, as in the herrings, the genus Clupea, is there a sternum present, which, as it consists of parts that belong to the dermal skeleton, might almost be called external: to it the extremities of the ribs are attached. Often, in addition to the ribs, there are little slender bones which are attached to the ribs or to the vertebree and lie amongst the muscles. These fine spines are named the ossicles of Artedi (spine epipleurales OWEN). The unpaired fins belong to the dermal skeleton and conse- quently have no relation to the morphological survey of the vertebrae. The caudal fin is usually attached to a triangular lamina which consists of the body of the last caudal vertebra and a connexion of the upper and lower spinous processes of some preceding vertebrae. The rays of the dorsal and anal fins are attached by means of a hinge-joint to small triangular flat bones, whose points are turned towards the vertebral column, and which may be named ¢nterspinal ossicles, since they lie between the spinous processes of the vertebree. Sometimes interspinal ossicles occur to which no rays are attached. The first interspinal ossicle of the anal fin limits the ventral cavity behind, and often unites with the inferior spinous processes of the first caudal vertebree to form a firm part in form of an arch}, The proper rays of the fins consist of two lateral parts, more or less coalesced ; some are formed of joints and towards the extremity split into branches. This applies equally to the rays of the ventral and pectoral fins’. The pectoral fins are the anterior limbs of fishes, and correspond to our arms or to the wings of birds. They are attached to an osseous belt, which, in the bony fishes and sturgeons, descends from the skull, in the sharks and rays from the spinal column, and 1 In some species of Chwtodon this bone is very thick, especially downwards. Here belongs that singular bone which OLAUS WorMIus described, “quod sua figura quasi murem representat,” Museum Wormianum. Amstelodami, 1655, folio, p. 271. Com- pare the figure of the skeleton of Ephippus gigas Cuv. in B. WouF Diss, inaug. med. de Osse peculiart Wormio dicto. Berolini, 1821, 4to. 2 Compare on the spines of the fins RoseNTHAL in Reru’s Archiv f. die Physiol. x. I8TI, 8. 359—372, with figs. ; FISHES. £7 unites beneath with that of the opposite side. Each half of this belt, which in osseous fishes is situated behind the gill-cover, consists of two pieces at the least. The uppermost is usually re- garded as a scapula; in most fishes it consists of two divisions, one placed below the other, of which the uppermost is situated like a scaly plate at the side of the head, and begins with two arms. The lower was by CUVIER compared with the upper arm-bone (humerus), but seems rather, as most writers conclude, to correspond to the clavicle (according to OWEN to the coracotd clavicle). Most anatomists are of opinion that the coracoid bone in the osseous fishes is represented by one or two bones, of which the lowest has the form of a pointed osseous style; this bone, or the uppermost when there are two, is attached to the upper extremity of the above- named osseous belt, and its lowest point, or the second bone, pene- trates obliquely backwards and downwards amongst the muscles’. Downwards are attached to the posterior margin of the osseous belt two, seldom three, small bony lamine. The two, which are usually present, may be regarded as the representatives of the bones of the fore-arm (radius and ulna); the third is probably a rudimentary upper arm-bone (humerus), which, however, as a rule, appears to be wanting in fishes. To the outer extremity of the two bony plates, compared to the radius and ulna, a row of four or five cylindrical or doubly- conical small bones is attached corresponding to the carpus. To these no metacarpal bones are attached?, but they sustain imme- diately the rays of the pectoral fins, which may thus be compared with fingers, but usually their number far exceeds that of the carpal bones. The ventral fins are attached to a triangular bone with the point directed forwards, which meets that of the opposite side in the mid-line of the abdomen, the two being almost always connected by suture. This bone represents the pelvis. Besides this, the 1 Os epicoracoideum of OWEN corresponding with the clavicle. Here OWEN recog- nises the homologue of an inferior vertebral arch (hemapophysis) belonging to the first vertebra. Lectwres, 1. 1. pp. 123, 160. 2 In Polypterus alone there is a row of small bones, which may be compared with the metacarpus, inserted between the carpus and the fin-rays, as also in the posterior limbs between the pelvic bones and the rays of the fins there lies a row of four long opicles, which might be named metatarsal bones. Compare on the pectoral fins C. METTENHEIMER, Disquisitiones de Membro Piscium pectoralt, VOL. II. 2 18 GLASS XIV. fingers alone of the posterior extremities are present, which cor- respond to the rays of the ventral fins. The comparison of the skull-bones of fishes with those of the skull of the other vertebral animals, is a rock upon which the ingenuity of many naturalists has been wrecked. The skull of bony fishes con- sists of a much greater number of bones than that of man; and this peculiarity may in part be explained on the supposition that what in the embryo state of man and mammals are distinct points of ossi- fication, in fishes persist as distinct bones during their entire life. Chiefly numerous are the bones which collectively represent the temporal bone in man}. On a superficial inspection the difficulty appears to be rendered still greater by the bones related to the largely developed tongue-bone and to the respiratory apparatus, which are connected with the bones of the skull. Moreover, some bones, which do not correspond to any in the skull of higher ver- tebrate animals, are to be referred to the dermal skeleton ?. At the base of the skull three bones are readily distinguished, placed in front of one another in a row; the basal piece of the occipital bone, the body of the sphenoid, an elongated bony lamina channelled above, and the vomer, which becomes broader and thicker forwards, and often on its under surface is armed with teeth. The basal piece of the occipital bone is a true body of a vertebra, and has behind a conical cavity for connexion with the first dorsal vertebra. Above it on each side lies a lateral occipital bone or articular portion (occipitale laterale, superior vertebral arch), which corresponds with the condyloid portion of the human occipital bone. These bones approach one another above, but leave between them and the basal piece below an aperture nearly triangular (foramen magnum), through which the spinal marrow passes into the cavity of the cranium; they are perforated by a conspicuous aperture, through which the nervus vagus, and a smaller one through which the n. glossopharyngeus, leaves the skull. Above the occipital foramen is an unpaired bone, which sometimes forms a sharp crest in the 1 On this bone, and on the skull of vertebrate animals in general, much that is interesting is to be found in the celebrated work of E. HattMANnNn Die vergleichende Osteologie des Schlifenbeins, mit 4 Kupfertafeln. Hannover, 1837, 4to. ? Without greater prolixity than this handbook permits we cannot offer more precise explanations of the names by which we describe the bones of the skull, and therefore must refrain also, for the most part, from criticising other designations of them. FISHES. 19 middle, and corresponds to the squamous portion of the occipital bone (crista occipitalis). It often separates the two parietal bones above, whence it was named by CUVIER the ¢nterparietal bone. At the side of this bone and above the lateral occipitals on each side is a small bone, which is also usually referred to the occipital bone, the os occipitale externum of CUVIER. BOJANUS regarded this bone as the petrous bone, because one of the semicircular canals of the labyrinth is covered by it'. But this circumstance affords no sufficient ground for such a determination, since, on account of their great development, the semicircular canals of fishes may be pro- tected by different bones. I rather suppose, with HALLMANN, that it is a part of the temporal bone*. Above the body of the sphenoid bone and immediately in front of the lateral occipital bones, there lies a flat bone on each side, ordinarily very large, and presenting a foramen or notch, through which the second and third branch of the fifth pair of nerves pass. These bony plates are the large ale of the sphenoid (0s alisphaenoideum OWEN’). On the skull above lie the two parietal bones, which ordinarily are small. Only rarely do they meet in the middle of the head at the upper part in a sagittal suture, as in Cyprinus. More in front, above the body of the sphenoid (which with OWEN we regard as formed of the bodies of two vertebree), are the two small wings of the sphenoid (orbito-sphenoidea), which follow upon the anterior margin of the large wings and mount up to the frontal bones. Under these wings through a membranous part the optic nerves proceed from the skull to the capsule of the eye. There are ordinarily two large frontal bones, distinguished by a median suture, which from the parietals and the occipital bone become narrower forward. Sometimes they are united to form a single bone, as in ‘the haddock and the cod; in some a crest is found here in the mid- line, which is a continuation of the occipital crest*; sometimes they 1 Bosanus Anatome Testud. Europ. p. 171. 2 (OWEN, parapophysis of the epencephalic vert., corresponding to the jugular process of the human occipital bone. | 3 MECKEL names this bone os petroswm, in which also HaLLMANN and STANNIUS concur. On its inner surface, at the inferior margin, lies the sac of the membranous labyrinth. * As in Lampris guttatus, Zeus luna GMELL., BAKKER 1.1. p. 171, Tab. 1. fig. III. @, in Vomer, &c. 2—2 20 CLASS XIV. are separated from each other by a membranous part (fontanelle), as in Orthagoriscus. Under the small or anterior wings of the sphenoid and the sphenoid, there is situated in the perch and many other osseous fishes an unpaired bone, which divides above mto two arms and rests upon the body of the sphenoid below. Cuvier names this part anterior sphenoid (rostrum ossis sphanoidet, sphenoide ante- rieur). More justly, as AGAssiz determines, may it be regarded as the eethmoid bone; in many fishes it remains cartilaginous. Above it joins the anterior and the large wings of the sphenoid!. In front of this and below the anterior portion of the frontal bones lies the nasal bone, a single bone, which is commonly described as the ethmoid (by Bosanus as the crista wthmoidalis). On each side of this are situated the so-named anterior frontal bones (frontalia ante- riora), which are small and closely connected with the nasal bone. An interposed bone (0s intercalare) may be observed on each side of the skull under the parietals and the external occipitals, which was named mastoid (0s mastoideum) by Cuvier. Often it is produced into a point at the back part of the skull. It may be compared to the squamous portion of the temporal bone, since the external occipital is rather to be regarded (p. 19) as the mastoid *. Tn this bone there is often on the inferior part a small bony piece, which is attached to the lateral occipital bone. It is present in the perch, for instance, but is absent in the pike. Cuvier supposes it to correspond with the petrous bone, which we think is not present in osseous fishes *; it is an accessory of the squamous portion of the temporal. Other parts of the temporal bone, which relate to the articulation of the lower jaw, belong to the bones of the face. The cranium is connected with the lower jaw on each side by a belt of different bones, which collectively make up the articular portion of the temporal bone. In the sharks and rays there is only a single cartilage on each side (suspensoriwm), which corresponds with the quadrate bone (0s quadratum s. tympanicum) of birds and 1 [Owen names this bone entosphenoid, as the common base of the two orbito- spheenoids: it is peculiar, as a distinct bone, to fishes. See Homologies, p. 44.] 2 [According to OWEN the squamosal is normally absent in fishes. Homol. p. 62 With Owen as well as Cuvier the bone in question is the mastoid. | 3 [See Owen Homologies, p. 28. The petrosal is the capsule of the labyrinth, and is never entirely ossified in fishes; if so, it belongs to the splanchno-skeleton. ] FISHES. aT reptiles. In the osseous fishes there are four or five bones on each side, of which the uppermost (epitympanicum OWEN) is connected with the skull (with the squamosal [mastoid OWEN] and posterior frontal) by articulation, whilst at the upper part behind it has an articular surface for the gill-cover (operculum). Under this bone is a flat osseous disc, often of a circular form; to this CUVIER gives the name of os tympanicum; behind it lies a styliform bone!, and under the two a triangular bony lamina with a smaller inferior extremity and an articular head, which is connected with the lower jaw. CUVIER names this the jugal bone. (In the batrachians the jugal bone runs from the upper jaw to the quadrate bone, and then forms a portion of the articular head for connexion with the lower jaw.) Behind this connecting arch there lies between the skull and the lower jaw the gill-cover, consisting of various bones, of which the first descends as an elongated curved bone nearly as far as the lower jaw. ‘This preoperculum seems to be simply a portion of the temporal bone, according to GEOFFROY SAINT-HILAIRE the proper os tympanicum, according to AGASsiz the styliform process (proces- sus styloideus”). The upper jaw-bones are commonly without teeth, and lie in the upper lip; they run obliquely backwards and downwards, with- out being connected at the extremity with other bones. ‘The inter- maxillary bones are, on the other hand, usually armed with teeth ; as are also the palate-bones, which are situated at the sides of the vomer. Behind each of these palate-bones lie two bones which are attached by cartilage to the jugal bone and the lamelliform middle portion of the quadrate bone, and may be aptly compared with the pterygoid processes that divide into an external and internal wing’. Below the orbits of the eye is placed a row of bony scales, quite external, which form a half-ring connected behind with the anterior frontal bone. Some writers regard these bones as parts of the jugal bone; but they belong perhaps to the dermal skeleton, and thus may be compared with the apparatus of the lateral line 1 Os symplecticum Cuvier, Tynypano-malleale AGAss1z, Meso-tympanicum OWEN. 2 [OwEN Homologies, p. 65. The opercular bones have no special homologues in higher animals. They form collectively the diverging appendage of the descending or tympano-mandibular arch of the third cranial vertebra. | 3 [OwEN Homologies, p. 114. The diverging appendage of the maxillary arch of the fourth, or anterior, vertebra of the head. | 22 CLASS XIV. (linea lateralis) for secreting mucus, as its continuation on to the head}. The anterior of these swb-orbital bones, which is also the largest, forms the outer or inferior margin of the nasal cavity. The superior margin of the sac of the olfactory organ is formed by a small plate of bone (the nasal bone according to CuVvIER), which also appears to belong to the dermal skeleton, and runs on each side of the anterior frontal bone to the bone of the upper jaw. It is the turbinated bone according to OWEN. The under jaw is divided into a right and left portion; these two halves are united in the middle by cartilage and ligamentous tissue alone. Each half usually consists of three pieces; an ar- ticular piece on each side (0s articulare), beneath it a small bony piece for the angle of the lower jaw (0s angulare), and an anterior piece, in which the teeth are fixed (the dental piece, os dentale), in the posterior margin of which is a triangular excisure for the recep- tion of the articular piece. We must next consider the tongue-bone, which presents a large development in the class of fishes, from its connexion with the gills, as an osseous respiratory apparatus. The body of the lingual bone lies under the head in the mid-plane, and usually consists of a series of unpaired bony pieces placed behind one another; forward, a cartilaginous or bony lamina penetrates into the tongue (glossohyale Grorrroy Satnt-Hiuarre). To these bony pieces five arches are attached, like ribs to a sternum. ‘The hindmost arc is incomplete, and is simply laid on the under side of the gullet; it consists on each side of a bone, which, on its upper surface, almost always bears teeth (the so-named ossa pharyngealia infertora). In some fishes (Scarus, Labrus) the two unite to form a single unpaired bone. The four anterior arches consist of several bony pieces, of which the uppermost mount up beneath the skull and bear teeth on their inferior surface (ossa pharyngealia supertora); the two middlemost, which are grooved beneath, bear the branchial lamine. At the side, and in front of the first branchial arch, two small bones are situated on each side, to which the horns of the tongue-bone are 1 Compare Stannius Ueber die Knochen des Seitenkanals der Fische, FRORIEP’S Neue Notizen, Bd. xxi1t. s. 97—100 (April, 1842). Of the same kind are certain bony plates, which in many fishes are situated laterally near the parietal bones, the ossa supra-temporalia of BAKKER and CUVIER. FISHES. 23 affixed, consisting of two flat bony pieces, that mount beneath the lower jaw, and are connected by means of a small styliform bone to the inner surface of the uppermost bone of the mandibular arch (epitympanicum), which connects the lower jaw to the cranium. A laterally compressed unpaired bone runs backwards from the union of the two horns of the tongue-bone, and is usually connected to the belt of the clavicles which sustains the pectoral fins. Beneath the horns of the tongue-bone is the so-named_ branchiostegous membrane (see above, p. 12), which completes the branchial aper- ture ; this membrane is supported by long ossicles bent backwards, called rays of the branchiostegous membrane, of which the number varies in different fishes, by which the generic characters may be compared; many fishes have seven such rays, the Cyprin¢ only three, where however they are broader. The three bony plates situated behind the preoperculum may be regarded as radiations from that bone corresponding to the bran- chiostegous rays from the horns of the tongue-bone. These plates form the gill-cover, the most external part of the bony apparatus for respiration. The largest of these pieces (operculum Cuy.) is a lamina attached to the epitympanicum, and forms the upper and outer edge of the branchial aperture. It has an irregular, more or less triangular, form ; beneath it les another small bony plate (sub- operculum Cuv.), and a smaller is placed in front of this below the preoperculum (interoperculum Cuv.). In the sharks, divided, carti- laginous radiations, like fingers, at the posterior margin of the os tympanicum, are met with, corresponding with the gill-cover; below they are repeated by similar appendages of the tongue-bone, which represent the branchiostegous rays. The sturgeons have no bran- chiostegous rays, but they have gill-covers like other fishes!. After this concise description of the skeleton, which in verte- brate animals must form the commencement of all anatomical sur- vey, we may proceed to treat of the remaining internal parts of fishes. The teeth, whose insertion upon various bones we have already indicated above, usually serve rather for seizing the prey and holding 1 This subject is excellently treated by H. RATHKE in Anatomisch-philosophische Untersuchungen iiber den Kiemenapparat und das Zungenbein der Wirbelthiere. Riga u. Dorpat, 1832, 4to. 24 CLASS XIV. it fast, than for dividing it. In form and number they present much variety in this class. In some fishes, as in the genus Acipenser, Syngnathus, &c. the teeth are entirely absent; in others, as the pike, they exist in great numbers in the lower jaw, the intermax- illary bone, the vomer, the palate-bones, the tongue, the branchial arches and the pharyngeal bones. ‘Teeth are rarely met with in the two upper jaw-bones that lie in the lip. The form is very vari- ous, sometimes that of laminze, mostly that of a cone, much like the corner teeth of mammals. Sometimes the teeth are as fine as hairs, as in the genus Chetodon. The mode of attachment differs, yet only seldom are they contained in sockets; ordinarily they are united to the bones by ligamentous matter alone or are coalescent with them by ossification. They are usually renewed constantly, and a regular replacement of teeth that occurs only once is met with in the mammals alone’. Salivary glands are not met with in the class of fishes. As a rule, these organs are more largely developed in animals that live on vegetable food than in those that make use of animal food; fishes live mostly on the last. Saliva also may more easily be dispensed with where no mastication is performed, and the food, as in fishes, is rapidly swallowed. There are, however, as in the sharks and yays, under the palate acinous glands, which secrete a slimy fluid; but these cannot be regarded as homologous with salivary glands. As little is there any excretory duct to the structure which in the carp is situated under the skull, in front of the ossa pharyngealia, which by some has been looked on as a salivary gland’, and of which the strong contraction under the action of various irritants has been announced by WEBER and MUELLER’. The tongue in most fishes is small, and possesses slight mobi- lity. The cesophagus commences like a funnel in the wide cavity 1 For obtaining a well-grounded knowledge of the teeth of fishes, the accurate and comprehensive work of R. OwEN, Odontography, London, 1840—1845, 8vo, pp. I—178, must be referred to. 2H. RaruKxe Beitrige zur Geschichte der Thierwelt, 11. Halle, 1824, 4to, s. I—7. Such a spongy tissue RATHKE found not only in Cyprinus, but also in Cobitis, Silurus, Belone, &c. (very small in the last-named genus); he is of opinion that it occurs uni- versally in those (osseous) fishes that have no appendices pylorice. 3 BE. H. Weser, in Murwter’s Archiv fiir Anat. u. Physiol. 1827, s. 308—3I1, regards it as an organ of taste. MuELLER found in it animal muscular fibre. Physiol. Il. 35. FISHES. 25 of the mouth, is usually very short, and furnished internally with longitudinal folds. It is often difficult to distinguish the stomach from the cesophagus, which directly passes into it, and to assign precisely the limit of the two. In some, as in the genus Cyprinus and in Cobitis fossilis, there is no distinction. The gullet (pharynx) is constantly surrounded by a layer of circular fibres, a true sphincter muscle, behind the ossa pharyngealia. In some fishes, as the pike, the stomach has an elongated form, wider in the middle, and the pylorus is situated at the posterior extremity, opposite to the superior orifice. In others the stomach is reflected at an angle or arch, the cardiac portion (pars cardiaca) being divided from the pyloric by a constriction, and the latter towards its extremity where it passes into the intestine is sensibly narrower, whilst the former preserves nearly the same width throughout. Such, for example, is the form of the stomach in Cyclopterus lumpus. ‘The most usual form however of the fish’s stomach is that where the cardiac portion is prolonged into a blind sac below, whilst the pyloric portion les transversely above this last on the right side of the stomach, like a narrower portion of intestine; such a stomach is found for instance in Lophius piscato- rius, Sctena aquila, &e., and, amongst our fresh-water fishes, in the perch. The muscular membrane of the stomach is always thinner than that at the commencement of the cesophagus, and con- sists of longitudinal and circular fibres. With very few exceptions there exists at the pylorus an annu- lar fold or membranous valve, which indicates the commencement of the small intestine. The distinction between the small and the large intestine is not always very obvious; the circumference of the posterior part of the intestine is not always larger, sometimes even smaller than that of the so-called small intestine. Almost never is there to be found a trace of a coecum at the commencement of the large intestine, but often (at least in the osseous fishes) an annular membranous valve, like that of the pylorus, is met with at the termi- nation of the small intestine. The intestinal canal is of very various length, more or less convoluted ; on the whole, however, it is short. In Petromyzon, Syngnathus, Belone, and some others, it holds an entirely straight course, without any flexure from the mouth to the vent. In the sharks and rays also the canal is short, but here a membranous valve of a spiral form, present also in the sturgeons 26 CLASS XIV. and Polypterus', enlarges the absorbent surface and delays the pas- sage of the food. In the sturgeons this spiral valve extends to the anus. Usually it is turned obliquely, like a staircase, but in Zy- gena, and some other sharks, it is attached lengthwise to one side, and is convoluted on itself, so that, when unrolled, it appears like a broad lamina’. The internal surface of the mucous membrane of the intestinal canal usually presents longitudinal projecting lines or folds, which often have a sinuous edge, or are incised transversely, or are united like a net, as in Lophius piscatorius. Only in very few fishes do true villi occur, like those commonly met with in the small intestine of the higher vertebrates. The position of the anus is very various. When fishes have a ventral fin it lies behind this, more or less remote from it. In the jugular fishes (p. 13), and such as have no ventral fins (apodes), the vent is situated below the gullet, and the intestine towards its ter- mination bends directly forwards, as for instance in the genus Ster- narchus. In some Pleuronectes (Solea) a part of the intestinal canal lies external to the abdominal cavity, or rather the abdominal cavity, with its lining of peritoneum, is prolonged behind the first interspinal bone of the pinna analis, which constitutes the osseous boundary between the ventral cavity and the tail®. The perito- neum has, in the Plagiostomes and some osseous fishes, two aper- tures near the anus which conduct outwards (port abdominales), by which in these last-mentioned the eggs and the sperma are dis- charged; the internal sexual organs lie with the intestinal canal in the sac of the peritoneum. External to and behind, or rather above, the peritoneum lie the kidneys and the swimming bladder upon 1 In the so-named (/anoids. See a figure of the intestinal canal of Polypterus bichir in J. MUELLER’S notice of this fish, Abhandl. der Konigl. Akad. der Wissensch. zu Berlin, Physik. Klasse, 1844, Tab. vt. fig. 1. In Lepidosteus also MUELLER observed an indication of the valve in the intestinal canal at the lower part; ibid. p. gr. 2 MEcKEL’S System der vergl. Anat. Iv. 1829, s. 35, in Zygena; in Galeus Thalassi- nus (Thalassorhinus vulpecula), and Glaucus, DuveRNoy Ann. des Sc. nat. sec. Série, Ill. 1835, pp. 274—284, and STEENSTRA Toussaint Tijdschr. voor nat. Geschied. er Physiologie, X. 1843, pp. 103—107, Pl. 3. (According to MUELLER and HENLE this arrangement occurs commonly in Zygena, Carcharias, Galeocerdo and Thalassorhinus.) 3 Numerous figures of the stomach and intestinal canal, in different fishes, are to found, amongst others, in Homr’s Lectures on comp. Anat. 11. Tab. 85—97, and espe- cially in RATHKE Beitrdge zu Gesch. der Thierwelt, 11. Tab. I—Iv., and in his memoir on the intestinal canal of fishes in MUELLER’S Archiv, 1837, 8. 335—356, Taf. 17—19. FISHES. a the spinal column. The productions of peritoneum by which it is connected with the lamina that surrounds the intestine, are mostly filaments or narrow bands remote from each other, and only rarely form a mesentery. In these productions, and also in the free folds of peritoneum, which may be compared with the omentum, there often lies a larger or smaller quantity of very white and soft fat. The blind appendages (cawca, appendices pylorice) deserve a special notice, which are attached to the intestinal canal in the neighbourhood of the pylorus, and in which a tenacious, slimy fluid is secreted. They are wanting in the Plagiostomes and Cyclostomes, in the Plectognathe and Lophobranchte, as also in some common bony fishes, as in the pike and in the carps (the genus Cyprinus L.). When present they differ much in form, size, and number. Poly- pterus and Ammodytes tobianus have only one such appendage, Lophius piscatorius has two, the perch three, in Zrigla five or more are counted, nine or ten in Sciena aquila, and they are still more numerous in the genus Gadus, in the herrings and salmons. When they are numerous they sometimes unite at their insertion in the intestinal canal to form common ducts, so that there are fewer openings into the intestine than blind appendages. Sometimes they are collected into bundles and connected by cellular tissue, as in Aiphias gladius', and in the sturgeons, where they form a gland- like body with a single efferent dice Accordingly these append- ages have been usually regarded as supplying the office of a pan- creas, which in the sharks and rays presents itself in the ordinary form. In the pike the pancreas, as a long whitish-yellow gland, lies along the left side of the stomach, connected with the liver by many short vessels, and covered by it. In the pike the pancreas, as a longitudinal whitish-yellow gland, lies along the left side of the stomach, connected with the liver by many short vessels, and covered by it. Also in the eel, Murana anguilla, a pancreas is found, which, as an elongated reddish-white mass terminating in a point backwards, lies upon the intestinal canal, and delivers its 1 RosentHaL Abhandlungen aus dem Gebiete der Anatomie, Physiol. und Pathologie. Berlin, 1824, 8vo, s. 79. The branches of these bundles unite here to form two stems, which are inserted close to the pylorus. 2 Observationes anatomice Collegiit privati Amstelodamensis. Amstelodami, 1673, 12mo, pp. 17—24, Tab, 11.; Monro Struct. and Physiol. of Fishes. Edinb. 1785, fol. 1G ao-¢ 28 CLASS XIV. secretion by two ducts close to the duct of the gall-bladder*. In Cyprinus E. H. Weer had found a duct close to the” ductus choledochus, opening into the intestine, and dividing into branches in the liver, but containing no bile’. Since however in the in- vestigation of fishes that have appendices pylorice a distinct pan- creas has lately been discovered in addition®, it would seem that the opinion which assigns to these appendages the place of this gland can no longer be maintained; probably, however, they also secrete a fluid that assists in the conversion of the food; for that they merely supply the intestine with a larger surface for absorp- tion, at least where they are closely collected into bundles or divided into branches, is not easily to be imagined*. In Lepidosiren the appendices pylorice and the pancreas are wanting. Fishes have a large, soft liver, saturated, as it were, with oily fluid. It often extends far backward in the abdominal cavity, and sometimes fills the spaces between the convolutions of the intestinal canal, as in the molluscs. In many fishes it lies more to the left than the right side. Its form is very various; when it is divided into lobes the number of these is very different, mostly, however, two, which are united by a small strip. In Myaine the liver consists of two portions quite distinct from each other. The gall- bladder is absent in very few species only of fishes; commonly it is large. Its duct, or the gall-bladder itself, receives the hepatic duct from the liver and penetrates the intestinal canal mostly close to the pylorus. The venous blood of the intestines is carried by three or two trunks, or by a single larger trunk, and usually by smaller branches in addition, to the liver. The venous blood from the swimming bladder, and in some fishes that also which returns from the organs of propagation, also flows to the liver before returning to the heart’. 1 Observat. anat. Coll. privat. Amstel. 11. p. 35, Tab. vill. fig. 1; F. G. MIzREN- porrr De Hepate piscium. Berolini, 1817, 8vo, p. 50, fig. z. 2 Mecke.’s Archiv f. Anat. u. Physiol. 1827, 8. 294—299, Tab. Iv. fig. 22. 3 In Acipenser Sturio by ALESSANDRINI, Ann. des Se. nat. Tom. xxix. 1833, pp- 193, 194, and lately by STANNIUS, in many fishes of different families. MUELLER’S Archiv, 1848, 8s. 405—407. 4 Very rarely, if ever, has chyme been found in the appendages. 5 Compare on the liver of fishes, besides the work of MIERENDORFF cited above, H. Raruxe in Mecxen’s Archiv f. Anat. u. Physiol. 1826, s, 126—152, and in MUuELLER’S Archiv, 1837, 8. 468—475. FISHES. 29 The spleen is absent in the Cyclostomes and Lepidosiren alone. It is of a blood-red colour, lies mostly on the right side, close to the stomach or the anterior portion of the intestine, and has sometimes one or more parts distinct from it (accessory spleens). In the perch it is placed as a narrow, elongated mass, within the first convolu- tion of the intestine; in the pike it lies behind the stomach, which it surrounds like a hood. In Squatina two spleens occur, a smaller, elongate and oval, in the neighbourhood of the pancreas, and another circular, placed on the stomach at its lower part. In Zamna and Carcharias there are several spleens distinct from each other. The lymph-vessels of fishes were first described by Hrwson and A. Monro (in 1769 and 1770). According to the researches of FOHMANN, who, some years ago, described and figured them more completely, they consist of a simple membrane, resembling serous membrane, and very smooth on the inside. They have no valves, except where the larger stems empty themselves into the veins. These larger stems fall into veins which may be compared to the subclavian veins. In addition there are still other communi- cations between smaller lymph-vessels and venous branches. The chyle, at least in the rays, is of a grey colour. Neither in the mesentery nor elsewhere are conglomerate or lymphatic glands met with in fishes’. The venous trunks, which return the blood from the different organs, conduct it to a large venous sinus situated between the peri- eardium and the membrane which supplies the office of diaphragm, and is properly nothing but the anterior part of the peritoneum strengthened by some tendinous filaments. The auricle, on the other hand, les in the pericardium with the ventricle, and is ordinarily broader than it. At the opening of the auricle into the ventricle valves are situated which prevent the reflux of the blood. The heart of fishes is small, and its weight forms ordinarily only Zoo, sometimes only zooq part of the weight of the whole body. It is situated behind and between the gills, in osseous fishes under the head, above the junction of the two clavicles (see above, p. 17). The muscular substance of the heart is of a red colour, although the voluntary muscles, as is well-known, are pale or even white. 1 Foumann, Das Saugadersystem der Wirbelthiere, Heft 1. Heidelberg u. Leipzig, 1827, fol. 30 CLASS XIV. In the osseous fishes the heart is more elongated, conical, in the rays and sharks broad. Its walls are very thick, and the muscular fibres are arranged in two layers, which sometimes separate from each other after death. Commonly not more than 20 or 30 beats of the heart are counted in fishes in a minute, whilst in birds 100 and more occur in the same period. The irritability of the heart continues long after death ; it beats, too, often for hours after it has been removed from the body. From the anterior part of the heart arises a single arterial stem. In the osseous fishes it commences with a conical thickening (bulbus); in the Cyclostomes this thickening is absent. At the origin of this arterial stem are semilunar valves, commonly two in number, which prevent the return of the blood into the ventricle after its contraction. In the sturgeons, the Plagiostomes, and, ac- cording to the investigations of MUELLER, in Polypterus and Lepi- dosteus also, the muscular substance of the heart is prolonged into a cylindrical part before the origin of the arterial stem, and in that cylindrical appendage (a true elongation of the ventricle) are many valves arranged in three or more longitudinal rows’. The continuation of the arterial stem now comes to view from the pericardium, and distributes itself as branchial arteries to the respi- ratory organs. The heart of fishes is thus venous alone, and in a physiological point of view is to be compared to the right ventricle of the human heart, whilst the arterial stem, conducting the venous blood to the gills, agrees in function with the pulmonary artery. But it does not follow from this that the heart of fishes corresponds also, in the view of comparative anatomy, to the right ventricle of birds and mammals. ‘he metamorphoses of frogs and salamanders, and the development of the embryo of the higher matter, must here afford the illustration. ‘This comparison teaches us, that from the heart, originally still undivided, there arise on each side different arterial arches, and that the pulmonary arteries are at first only branches of the hindmost of these arches. Thus in fishes the branchial arteries are to be compared to the arterial arches of the embryonal state. But, instead of immediately bending round to form the aorta, they separate into branches and 1 The work of F. TrrpEMANN, Anatomie des Fischherzens, mit 4 Kupfert. Landshut, 1809, 4to, contains many details on the heart of this class. FISHES. 31 a fine network of capillaries on the gills. From this the roots of the branchial veins arise, which mounting along the branchial arches, afterwards unite to form the large artery. Hence in fishes a system of capillaries is placed between the heart and the aorta; and this is one of the most characteristic peculiarities in the anatomy of this class. Already from the branchial veins, before they unite to form the aorta, certain arteries arise especially for the head. In the bony fishes the branchial veins of each side first unite to form a vein (vena branchialis communis), and pass backwards into the aorta, whilst, according to the discovery of Hyrtt, they are united in front by a transverse vessel, and thus form an arterial circle (circulus cephalicus) beneath the cranium*. The arteries (arterie axillares) for the anterior limbs (pectoral fins) are, in Torpedo and Chimera, provided with a muscular covering and expanded into lateral hearts?. In Amphioxus lanceolatus, where the heart is not enclosed in a pericardium and is tubular, contractile swellings have also been observed on the branchial arteries, and, moreover, on each side a pulsating arch, which passes immediately from the heart to the aorta’, The venous system also of fishes may be illustrated by the history of development in higher vertebrate animals. This teaches us that originally there are two anterior and two posterior venous stems which conduct the blood back to the heart. The anterior are the persistent ven jugulares ; the posterior, which, at a later period, when the cava is developed, in great part disappear, are named by RATHKE vene cardinales. On each side the anterior and posterior venous stems meet in a transverse canal (Ductus Cuvierd), which 1 Similar in form to the arterial circulus Willisti within the human skull.—The work of Hyrtt on the vascular arrangement of fishes (Medic. Jahrb. der Gstterr, Staates. Neueste Folge, Bd. xv. 1838) is known to me, and perhaps to many others, from citations alone. Compare also on this subject, J. MuELLER in Abhandl. der Kénigl. Akad. der Wissensch. zu Berlin, aus d. J. 1839, Vergl. Anatomie der Myxinoiden, dritte Fortsetzung. This entire work is published separately, Berlin, 1835 and 1841. 2 According to J. Davy in Torpedo, Phil. Trans. 1832, p. 259; according to the investigations of DUVERNOY, and afterwards of VALENTIN in Chimera, Ann. des Sc. natur., sec. Série, VIII. 1837, pp. 35—41, MUELLER’S Archiv, 1842, 8. 25. 3 Here also the portal vein and the cava are pulsating tubular hearts. See MUEL- LER Ueber den Bau und die Lebenserscheinungen der Branchiostoma lubricum. Abh. der Konigl. Akad. der Wissenschaft. zu Berlin aus d. Jahre 1844. By CLASS XIV. unites with that of the opposite side, and thus conducts the blood to the auricle of the heart. What, therefore, is thus seen in the embryonal state of other vertebrate animals remains in fishes as the permanent form. There are properly no posterior cave, which in fishes are usually so named, but venous stems which correspond to the vene cardinales of the embryo, and of which in osseous fishes that of the right side is usually much the most developed, so that a single posterior cava alone is ascribed to them. ‘The venous stem, or the veins that come from the liver (vena hepatica or vene hepatice), join the common venous sinus into which the two ductus Cuviert open. The hepatic veins alone are those that can be compared with the posterior caval. In Anguilla and Murenophis the veins of the caudal fin unite to form a pulsating venous heart on each side of the last caudal vertebra?. In Myaine the portal vein is distended into a large sac, which contracts and expands alternately*. In fishes, as in other classes of animals, arterial and venous plexuses (retia mirabilia*) occur, in which the stem is suddenly lost as it were, and of which the vessels at first lie side by side without dividing into branches, but afterwards either pass into capillaries or unite to form one or more larger trunks. ‘They occur in the vessels of the viscera in Thynnus and some sharks, also in the swimming bladder of 1H. Ratuxe, Veber den Bau und die Entwickelung des Venensystems der Wirbel- thiere; dritter Bericht tiber das Naturwissensch. Seminar zu Koénigsberg. 1838, 4to. 2 According to the discovery of MarsHAaLL Hatin the eel; according to MUELLER, in Murenophis also. At the same part many osseous fishes have a sinus, which belongs to the lymphatic system of vessels. See Hyrrn in MUELLER’S Archiv, 1843. s. 224— 240, with fig. 3 MUELLER’S Archiv, 1842, s. 477. 4 In Thynnus vulgaris and Thynnus brachypterus the veins from the stomach, the intestinal canal and the spleen, before entering the liver, form very large retia mira- bilia of pencil-shaped branches, from which subsequently larger veins arise as portal branches; the artery that goes to the abdominal viscera (arteria celiaca) distributes its blood by such nets alone to the stomach and the intestinal canal, but to the liver by an hepatic artery not deviating from the ordinary form. D. F. Escuricut u. J. MouziiEr Ueber die arteridsen und venisen Wundernetze an der Leber des Thunfisches (Abh. der Akad. der Wissensch. zu Berlin, 1835). In Lamna cornubica such arterial and venous networks are met with, here formed by the hepatic veins; in Carcharias vulpes there are venous and arterial retia m. of a pennate form on the stomach and that part of the intestinal canal where the spiral valve is situated: see A. Bantu Diss. inaug. de Retibus mirabilibus, Berolini, 1837, 4to, after observations of J. MUELLER. FISHES. 33 many fishes; the red, apparently glandular body, that in most bony fishes surrounds the entrance of the optic nerve into the ball of the eye at the choroid coat (glandula choroidalis), is merely such a vascular network. The respiratory organs of fishes, the gills, consist in most of small leaflets usually triangular and of equal breadth, attached by their bases to the branchial arches on which the branchial arteries ramify. ‘These leaflets mostly form two rows on each branchial arch ; if one such row alone be present, then the name of half-gill is given to such anarch. In the bony fishes and the sturgeons the branchial arches are on the outside free; the water is taken in by the mouth and afterwards expelled by two gill-apertures behind the gill-covers (one on each side). In the sharks and rays, on the contrary, there proceeds from each branchial arch, between the branchial leaflets of the anterior and posterior row, a membranous production as far as the skin, entirely covering the gills in these fishes, excepting five apertures for the expulsion of the water; hence arise complete partitions between the pharynx and the skin, in which the branchial arches are situated. The posterior wall of the fifth gill-cavity is here without branchial leaflets. The leaflets are cartilaginous internally, or rarely bony, and are covered with a rich vascular net, so as to have a bright red colour’. The entire apparatus is covered by a continuation of the mucous membrane of the mouth. In the respiration of fishes the air contained in the water is alone effectual, and by no means the oxygen of the water, which is not decomposed by this function. Some fishes mount to the surface of the water to breathe atmospheric air itself, and they die when this is rendered impossible by gauze interposed. But fishes cannot live long out of water; some die even very rapidly, because the leaflets fall together and cohere, so that the circulation of blood in these organs is interrupted, and the oxygen of the air cannot act upon the parts that thus cover each other?. With the half-gills or the accessory gills, which in the stur- geons occur on the gill-cover, those false gills (pseudo-branchie) 1 DOELLINGER gave a very beautiful figure of this vascular net in Abhandl. der mathem. physik. Klasse der Akad. zu Miinchen, 1. 1837. Ueber die Vertheilung des Blutes in den Kiemen der Fische, s. 785—794, Tab. 1. fig. 3. 2 See FLouRENS Experiences sur le mécanisme de la respiration des Poissons, Ann. des Se. natur, XX. 1830, pp. 5—25. VOL. II. a) 34 CLASS XIV. must not be confounded which in many fishes are found on the palate, above and outwards from the gills, sometimes presenting a more glandular lobulated structure, but mostly a pennate or pecti- nate form with a single row of leaflets. Since these organs receive arterial blood, they cannot be for respiration. The blood that returns from them unites with that of an arterial branch (arteria ophthalmica magna) which supplies the choroid coat of the eye-ball, where usually it forms a rete mirabile, which, connected with a similar venous net for the blood returning from the eye-ball, forms the choroid gland lately spoken of, and which usually occurs simul- taneously with the false gill’. As little as this organ does the swimming-bladder of fishes deserve to be regarded as serving for respiration®. ‘This bladder occurs in the sturgeons and many osseous fishes, and is situated above the intestinal canal towards the spine, but under the kidneys, almost always as an unpaired symmetrical organ. Its walls are formed by two membranes; an external tendinous membrane and an internal thin mucous membrane, richly supplied with vessels and covered with flat epithelium on the inner surface. In addition, this bladder is invested on the ventral surface with a production from the peritoneum. In some fishes a duct proceeds from it to the cesophagus or to the stomach; in some there is a fissure, as a species of glottis, which leads immediately from the cesophagus to the swimming-bladder. Since the swimming-bladder comes into being as an eversion of the intestinal canal, it is probable that even in cases where it is quite closed a canal existed at an earlier period, which has been condensed to form a ligament, or has been entirely absorb- ed. In many fishes, in most SL Felitts especially, the swimming- 1 Compare J. Muruurr Abhandl. der Akad. der Wissensch. zu Berlin, aus d. Jahre 1839, S. 213—240, 247—261. 2 There are very numerous publications on this organ, of which we are content to notice the following: G. FiscHer Versuch iiber die Schwimmblase der Fische, Leipzig, 1795, 8vo; DE La RocuE Observations sur la vessie aérienne des Poissons, Ann. du Mus. X1v. 1809, pp. 184—217, pp. 245—289 ; H. RatHKEe Bemerkungen iiber die Schwimmblase einiger Fische in his Beitriége zur Gesch. der Thierwelt, 4te Abth. 1827, s. 102—120, and his later investigations in MuELLER’S Archiv, 1838, s. 413 —445, Taf. 12; K.E. Von Barr Untersuchungen iiber die Entwickelungsgesch. der Fische, nebst einem Anhange iiber die Schwimmblase, Leipzig, 1835, 4to; H. 8S. R. Jacost De vesica aérea Piscium, Diss, inaug. Berolini, 1840, 4t0, under the auspices of J. MUELLER. FISHES. 35 bladder is entirely closed. A few fishes have a cellular swim- ming-bladder, by which Lepidosteus in particular is distinguished. The form of the bladder is usually elongate; sometimes provided at the anterior extremity with lateral blind appendages; sometimes with a row of such appendages extending the whole length on each side. In some fishes it is constricted in the middle, and divided into two chambers lying one behind the other. The blood-vessels divide in a fan-like form into fine branches over the internal mucous membrane, or form retia mirabilia at particular points, which have been described as red glandular masses. Formerly it was thought that such nets are absent in fishes whose swimming-bladder is pro- vided with a duct; but this, however, is not a general rule’. The air contained in the swimming-bladder consists of a mix- ture of oxygen and nitrogen, with sometimes a small quantity of carbonic acid gas. In fishes of the same species chemical investi- gation often indicates remarkable differences. According to Bior and De La Rocue, the quantity of oxygen increases with the depth m which the fishes live; thus in general it is much more abundant in marine than in fresh-water fishes; in the last a con- siderable quantity of nitrogen is always present, and in the carps it has even been supposed that the air of the swimming-bladder con- sists of this gas alone; in marine fishes the air of the bladder may contain even eighty per cent. of oxygen gas. This air is secreted by the inner surface of the swimming-bladder, as appears from those fishes that have the bladder entirely closed; but even in those whose swimming-bladder has a duct, it is difficult to suppose, as RatHKE has suggested, that the air penetrates into the bladder from without. More probably the duct serves for the escape of the air. | Opinions differ respecting the use of the swimming-bladder in the animal economy of fishes. The name that has been given to it indicates the presumed connexion with swimming. ‘This is the common opinion, first advanced by BoRELLI, according to which the fish by compression or expansion of the bladder can make itself specifically heavier or lighter, and alternately sink and rise in the 1 For further particulars on these blood-glands of the swimming-bladder, see J. Murtier Abhandl. der Akad. der Wissensch. zu Berlin, a. dem Jahre 1839, s. 262 —2'5. 3—2 36 CLASS XIV. water. This compression is effected by motions of the ribs, whilst in addition sometimes proper muscles are present in the swimming- bladder’. But in many fishes it is difficult to shew how they are in a condition to expand the bladder and to rarefy the air. Whatever opinion, however, be entertained respecting the use of the organ, it is difficult to explain why, if it really exerts an important influence on the life or the economy of fishes, it should be absent in so many species, and even in some genera of fishes should be present in certain species whilst in others of the same common form it is not found. Certain it is that a bladder filled with air will render specifically lighter the body of the fish, which, without it, is only a little above the specific gravity of water; and since it is placed near the back, that part especially of the body which in other respects is the heavier, so that the centre of gravity of the fish will sink, and its turning belly upwards be prevented. Deep-bodied, compressed fishes have also usually a well-developed swimming-bladder. According * to the experiments of MUELLER, however, the fins and especially the vertical fins (dorsal and anal fin) principally resist this upset- ting. In some fishes, according to the discoveries of E. H. Wrser, the swimming-bladder is in connexion with the auditory apparatus, as an organ that intensifies and conducts sound. That this bladder is a second respiratory organ and to be compared with the bladder- like lung of certain reptiles, as some suppose, is sufficiently refuted. by the course of the blood-vessels; for if this were true it would receive venous and not arterial blood’. The secretion of urine is effected by two kidneys, lying upon the spinal column, which are often united with each other at their posterior extremity. In most osseous fishes they extend from the head backwards as far as above the anus. They are usually of a loose spongy tissue; here the difference between internal 1 In some of the Siluride (Auchenipterus, Huanemus, Synodontis, Doras and Mela- pterurus) there is a bony lamina that descends obliquely on each side from the first vertebra to the swimming-bladder, and compresses it like a spring. This lamina can be raised by a muscle arising from the cranium, on which the bladder expands. See J. Mueuier Abhandl. der Akad. d. Wissensch. zu Berlin. a. d. J. 1842. 2G. FiscHER modifies the opinion that the swimming-bladder is a respiratory organ in this way: it is for the respiration of the air contained in the water, whilst the gills serve for decomposing the water; but in the respiration of fishes the water is not decomposed, as has already been noticed above, FISHES. a” and external substance (substantia corticalis and medullaris) does not exist. The entire substance of the kidneys is formed of ccecal tubes which open into the ureters. These usually coalesce in a bladder, or become wider at their inferior extremity. The bladder is situated upon the rectum and the wrethra opens behind this’. Renal capsules (renes succenturiat’, capsule renales), formerly thought to be absent m fishes, occur in the cartilaginous fishes as narrow, elongated, yellow bands situated on the inner side of the kidneys, and in the bony fishes usually as two small, round, whitish bodies, mostly at the posterior extremity of the kidneys’. The organs of propagation of fishes are on the whole not very composite. The sexes are always distinct, but often, as in the lower animals, there is a great similarity between the parts that prepare the germ and the seed (ovaries and testes). Sometimes the entire appara- tus of the organs of propagation is limited simply to these indispen- sable and essential parts. Ordinarily there are two ovaries present and two testes; there are however fishes in which these organs are unpaired, of which the examples are more frequent in female speci- mens. One ovary alone is developed in the perch, in Blennius viviparus, Ammodytes tobianus, Cobitis barbatula, Cobitis tenia; in many sharks also (Scylliwm, Carcharias, Sphyrna, Mustelus and Galeus) only one ovary is present, mostly situated on the right side. In most bony fishes the ovaries form two long and large sacs, which lie on each side near the intestinal canal and the liver (the so-called roe). From the inner surface folds arise which ordinarily form transverse partitions; in these folds the eges are developed, which in some fishes are exceedingly numerous in the spawning-season, sometimes some hundreds of thousands. The inferior part of the ovary is without such plates, and serves only for transmitting the eggs; thus it may be named an oviduct; and here 1 See on this subject A. J. D. SreenstRA Toussaint Commentatio de systemate uropoetico Piscium, Ann. Acad, Lugd. Bat. 1835. The opening of the urethra behind the anus is a special characteristic peculiarity of fishes. From this fact RATHKE and V. Bakr concluded that the kidneys of fishes do not correspond to those of the higher vertebrates, but to the embryonal corpora Wolfiana (the primordial kidneys). In the embryo of fishes at least no corpora Wolfiana, except these kidneys, are met with. H. RATHKE in Burpacu’s Physiologie, 1. s. 569; V. Baur Entwickelungsgesch. der Thiere, 11. 1837, 8. 314. 2 Comp. STANNIUS in MUELLER’s Archiv, 1839, s. 97—101, Taf. Iv. 38 CLASS XIV. we find a disposition which in the invertebrate animals is normal, but in the vertebrates does not occur elsewhere, namely that the oviduct is an immediate continuation of the ovary. The two ovi- ducts afterwards meet in a single canal which opens in front of the urethra behind the anus in a small groove, sometimes on a papilla. In other fishes (the eels, the salmons, the Cyclostomes) the ovary consists of an elongated lamina, which is attached to the spinal column by a duplicature of peritoneum, and has many projecting folds; oviducts are not present; the eggs developed in these folds are detached when ripe, fall into the cavity of the abdomen, and escape by one or two ventral apertures’. In the Plagiostomes and in Chimera the ovaries are much smaller than in the rest of the fishes; they lie in the anterior part of the abdominal cavity near the liver, and form bunches as in birds; whilst some eggs on the surface are more developed, others as smaller granules Hie conceilole in the stroma. Here there are always two oviducts, even when there is only one ovary. These have a common opening near to or in front of the ovaries, and are by no means immediately connected with them as in the bony fishes. They are very long, provided internally with longitudinal folds, and become wider at the lower part. Above the widening a glandular tissue is situated which surrounds the oviduct as an annular swelling; it is more developed in those which are oviparous, and consists of many ccecal tubes, laid close toge- ther, which open into the oviduct®. In the viviparous sharks the inferior wider part of the oviduct may be named uterus, which thus is double, as in the marsupial animals and the ornithorhynchus in the class of mammals. The testes (in the bony fishes named m7/é) are in the male in- dividuals placed in the same situation as that occupied by the ovary in the females. They are larger in this class than in any other vertebrate animals, and the secretion of sperma is as abundant as the eges are numerous in the ovariwm. On the inside of each of 1 See a figure of the ovarium of the salmon in Carus Tabula anatom. comparativam illustrantes, Fasc. v. Tab. rv. fig. vit. ; of Petromyzon marinus in Catalogue of the Series of compar. Anatomy in the Musewm of the Royal College of Surgeons, Iv. Pl. 59; of the eel, ibid. Pl. 60, and in Honnpaum-Hornscuvucn Diss. inaug. de Anguillarum Seau et Generatione. Grijphiz, 1842, 4to. 2 In the rays J. Musnier has figured this part in his great work, De penitioré glandularum structura, Tab. It. figs. 14, 15. FISHES. 39 the testes runs tlte vas deferens, and the two unite to form a common canal, longer or shorter, which joins the urethra, and thus opens in a groove or on a papilla behind the anus’. In most osseous fishes the tissue of the testes consists of tubes, of which the blind extremi- ties are directed towards the outside of the organs, sometimes dividing there into two branches, and open on the inside into the efferent vessel*. In the eels* and in Petromyzon, on the other hand, the testes are flat bands like the ovaria, of a granular tissue. Hfferent ducts are absent; the seed is received by the abdominal cavity and escapes by an aperture behind the vent. In the Plagio- stomes the testes are of a vesicular tissue, and in these vesicles granules are contained which are filled with sperma. Fine ducts (vasa efferentia) run to the epididymes, situated behind the testes, and from these arise the two efferent vessels, at first very tortuous, afterwards straighter, which run over the kidneys and finally widen into two vesicule seminales, which are supplied internally with annular partitions. From these the seminal fluid is conducted to the penis, which lies in the cloaca. There are, in addition, behind the pelvis, near the tail, appendages which are supported internally by cartilage; they serve to embrace the female during copulation by affixing themselves to her tail*. Most osseous fishes do not copulate, but the males sprinkle the egos laid by the female with their seminal fluid. It is probable that 1 See a figure of the testes in Trigla lyra in the Tabule of Carus cited above, Fase. v. Tab. Iv. fig. 4. 2 This tubular structure, first observed by RATHKE, was afterwards more fully illustrated by TREVIRANUS and J. MUELLER. See TREVIRANUS Zeitschr. fiir Physiol. 11. Darmstadt, 1827, s, 1o—13, Tab. 111. fig. 4, MUELLER De penitior: glandular. struct. p. 104, Tab. xv. fig. 8. 3 According to SCHLUESSER, it is not improbable that the parts described by HoHn- BAUM-HOoRNSCHUCH as testes in eels, are only undeveloped ovaria, and that male eels are still unknown. G. ScHLUESSER de Petromyzontum et Anguillarum Sexu, Diss. inaug. Dorpati, 1848. 4 Compare TrevrrANUS Ueber die Zeugungsorgane des Dornhay, Zeitschr. fiir Physiol. 11. 1827, s. 3—10, Tab. 11.; STANNIUS in MUELLER’S Archiv, 1840, 8. 41— 43. On the sexual organs of fishes consult especially RaTHKE Beitr. zur Gesch. der Thicrwelt, 2te Abth. s. 117—206, and in MuELLER’S Archiv, 1836, s. 171—186, and on the development of these parts, Beitr. zur Gesch. der Thierw., 3te Abth. s, 1—18.—Also J. Murtier Veber den kirnigen Bau der Hoden bet mehreren Fischen, in TIEDEMANN and TREVIRANUS Zeitschr. f. Physiol. tv. 1831, s. 100—113, and H. Srannius Ueber die mannliche Geschlechtstheile der Rochen wu. Haien, MUELLER’S Archiv, 1840, 8. 41—43. 40 CLASS XIV. the males are attracted by the olfactory sense, by Which they collect around the females of their species at the season of spawning and come into their neighbourhood. Amongst those which copulate, some species are also oviparous. Only few bony fishes are vivi- parous, as, for instance, Anableps, Blennius viviparus. Of the carti- laginous fishes, on the contrary, amongst the Plagiostomes the Raje, in a proper sense, and the species of sharks of the genus Scyllium alone, are oviparous. ‘he egg in these rays and sharks has a tough, horny, flat, elongated shell, of which the four corners terminate in the rays in long tortuous filaments, wound round each other. The development of fishes is distinguished from that of the sealy reptiles, the birds and mammals, in that neither amnion nor allantois is formed. In the beginning that dividing or cleaving of the yolk is perceptible, which we have already spoken of in different classes of invertebrate animals’. When the yolk has again become smooth, the germinal disc appears, and as it grows spreads itself over the yolk until it quite surrounds it. After it has thus become a vesicle, or in other fishes even before this period, there arises, in that part of the germ-dise which is first formed, a longitudinal groove as the first commencement of the embryo. ‘Two projecting edges surround this groove and approach each other, whilst at the bottom of the groove the dorsal cord, as the first commencement of the skeleton (comp. above, pp. 5, 8), is formed. The innermost layer of the germ-membrane (the mucous layer) presents a constriction, and is thus divided into a canal situated beneath the dorsal cord and into a vitelline sac. In some fishes this vitelline sac is included in the ventral cavity with the intestinal canal by the walls of the abdomen, formed from the serous layer; there is thus an internal vitelline sac present in these, and the abdomen of the embryo presents an unusual projection (Cyprinus, Perca, Salmo); in others the abdominal covering is drawn together by constriction like the mucous layer, and the vitelline sac hangs on the outside of the ventral cavity, being attached to it by a short pedicle (Blennius * Observations on this subject, in eggs of fishes impregnated artificially, have been published by Ruscon1, MuELLEr’s Archiv, 1836, s. 278—288, Taf. xm. The eggs acquire an elevation or protuberance, and this, not the entire yolk, is the seat of the regularly increasing grooves. Later observations have shewn that this phenomenon depends upon the development and change of the germinal vesicle. FISHES. 41 viviparus, Cottus gobio, Syngnathus). In the Plagiostomes (sharks and rays) an external vitelline sac is similarly observed, which here, however, has a longer pedicle, which in some sharks is beset externally with vill’. In most of these fishes the umbilico-intestinal duct is continued within the abdomen into a second internal vitelline sac: a blind sac, which occupies a large part of the ventral cavity, and is inserted into the anterior bladder-like portion of the intestinal canal above the commencement of the spiral valve’. The lateral walls of the body of the embryo, which are at first smooth, suddenly present on each side 5 (or 6) fissures of equal width. Between these fissures four small streaks are formed as the commencement of the branchial arches. In front of the first fissure and behind the mouth arises a wider arch divided by a groove into two parts. The anterior half of this is changed into the under jaw and the various bony pieces which unite it with the cranium. From the posterior half arise the horns of the tongue-bone; at the posterior margin of these parts in bony fishes the gill-covers and the branchial rays are developed at a later period only, the branchial arches being at first unprotected. The unpaired fins arise at first as a long fold of skin, which surrounds the body, and is much more extensive than the future pinna dorsalis and analis. All the bony fishes whose development has been hitherto observed, quit their egg-covers at a very early period and whilst still imperfectly formed. In the embryos of sharks and rays the filaments which hang freely from the branchial fissures, productions of the internal leaflets of the gills, reminding us of the external gills of larvee of Salamanders, are especially deserving of regard”. 1 This vesicular part of the intestinal canal was named by CoLLINs bursa Entiana, after GEORGE ENTE, by whom it was first discovered; System of Anatomy, 1685, Tab. 33, fig. 2g. In Carcharias and Mustelus levis MUELL. an external vitelline sac alone is present, and this is attached by many folds to the inner surface of the wider inferior part of the oviduct named wferus. These sharks have thus a placenta, which however differs from that of mammals, and is formed by the vitelline sac. Compare especially J. Muewier Veber den glatten Hai des Aristoteles, &c. Abh. d. Akad. zw Berl. Jahrg. 1840, Phystk-math. Kl. s. 187—257, with fig. 2 On the development of fishes, amongst other works may be compared H. RaTHKE Abhandlungen zur Bildungs- und Entwickelungs-geschichte, 11. Leipzig, 1833, 4t0o, s. 1—68 (on the development of Blennius viviparus); V. BAER Untersuchungen tiber die Entwickelungs-geschichte der Fische, Leipzig, 1835, 4to; the same, Ueber Ent- wickelungs-geschichte der Thiere, 11. Kénigsberg, 1837, 4t0, s. 295—315; RaATHKE in Burpacw’s Physiologie, 2te Aufl. 11. 1837, s. 276—296; C. Voar Lmbryologie des 42 CLASS XIV. Let us now consider shortly those organs in fishes which have reference to the functions of animal life. Here in the first place the nervous system claims attention. Of this the central parts, the spinal marrow and brain, offer commonly a different relation to each other than in the higher vertebrates. The mass of the spinal marrow or cord, in proportion to that of the brain, is very large; the cord extends, with few exceptions, to the end of the vertebral column. Consequently a cauda equina is only seldom present: a disposition by which the last spinal nerves arising far from the place where they pass outwards from the vertebral column, and so also leaving the cord under a very acute angle, lie close together in a bundle’. On the under and upper surface the spinal cord is divided longitudinally by a fissure into two lateral parts. In the interior, through the entire cord, there runs a narrow canal which extends into the brain to the fourth ventricle, into which it expands. The brain is small, not only, as we have said, in proportion to the preponderant spinal marrow, but also to the whole body, of the weight of which it commonly forms less than the zoo th or even the goo th part. This small magnitude of the brain may be inferred from the smallness of the cranial cavity, though even this, at least in bony fishes, is still much larger than the brain which it includes. For there remains between the delicate membrane which immediately covers the surface of the brain and the hard membrane that covers the inner surface of the cranial bones, a space which is occupied by a loose cellular tissue, a species of arachnoid, which is Salmones (Coregonus palwa, Cuv.) in AGASSIZ Hist. natur. des Poissons d’eau douce, 2 Livr., Neuchatel, 1842 ; Duvernoy Sur le développement de la Poecilie de Surinam, Ann. des sc. natur., 3iéme Série, 1. 1844, pp. 313—360. Pl. 17. On the development of rays and sharks may be consulted, RavuKE Beitrdge zur Gesch. der Thicrwelt, rv. 1827, s. 4—66, and F. S, Lrucxarr Untersuchungen tiber die dusseren Kiemen der Embryonen von Rochen u. Hayen, Stuttgart, 1836, Svo. * In the sun-fish (Orthagoriscus), according to ARSAKY, andalso in Diodon, accord- ing to OWEN (Lectwres on Comp. Anat. 11. p. 173), there is a very short, conical spinal cord, with a cauda equina; in Lophius the cord is also short, but extends as far as the twelfth vertebra ; here also there is a cauda equina, which in part covers the spinal cord. 2 In a pike the cerebral mass was found to be >31,< of the weight of the body; in a sheat-fish, scheidfisch or sly silurus (silwrus glanis), only qels7 of it. Comp. Harrier Elem. Physiol. 1v. pp. 5, 6, and Cuvier Leg. d’ Anat. comp. II. p. 152, where several examples are adduced, The weight of the brain in a full-grown man may be estimated at about 31, — 1. of the weight of the whole body, although such estimates cannot easily be rigorous, since the weight of the human body is so different in different individuals. FISHES. 43 - saturated with a fatty matter mostly in a fluid state. In younger fishes, however, the brain is relatively larger, and fills the cranial cavity in a greater degree than in older individuals. In breadth the brain exceeds the spinal cord but slightly, is flat and elongate, and consists of eight lobes partly in pairs, partly unpaired, lying behind one another. The unpaired part that lies in front of the medulla oblongata above the fourth ventricle, corresponds to the lesser brain or cerebellum; and, however various the opinions of different writers on other points, here there is the most perfect agreement. Internally this part is hollow, for the fourth ventricle at its upper part extends into it. In front of this cerebral mass lie two convex bodies, hollow internally, which in bony fishes consti- tute the largest division of the brain, whilst in the cartilaginous they are smaller, CAMPER, Cuvier, and amongst the latest writers GOoTTSCHE, compare these parts with the hemispheres of the larger brain (cerebrum), whilst others place them on a par with the corpora quadrigemina of man; HALLER regarded them as the thalami ner- vorum opticorum. In the bony fishes there lie in the interior of these parts and behind, two or four small round tubercles of grey substance, which are wanting in cartilaginous fishes. In these last the two convex bodies are also smaller, and in front of them lies an unpaired hollow eminence, open above (lobus ventricul? tertiz), which in the bony fishes does not appear as a distinct part. The anterior division of the brain in the osseous fishes is formed of two conical parts, not hollow internally, united by a commissure; from this division arise the long olfactory nerves (the first pair of nerves), issuing from the inferior surface, but fortified in most bony fishes by a swelling at the anterior extremity of these lobes, or by two such in Murena. In the Plagiostomes these anterior lobes, broad and hollow within, are united with one another. On the inferior surface of the brain the hypophysis or glandula pituitaria, some- times attached to a long pedicle, is seen, near to which on each side lies an oval or kidney-shaped eminence (the lod inferiores, the tubercula reniformia of HALLER’). 1 The origins of the optic nerves pass along the outside of these parts, and the third pair of nerves springs from their posterior margin. They are usually compared to the corpora candicantia of the brain of mammals, to which notion, however, well-founded objections have been raised by Cuvier. It were more prudent to regard them, with GOTTSCHE, as special parts peculiar to the brain of fishes. 44 CLASS XIV. The comparison with the brain of reptiles, and especially the history of development of the brain in higher vertebrates, which is most perfectly known to us in the embryo of the bird, induces us to recognise in the hollow lobes in front of the cerebellum in fishes the union of the corpora quadrigemina and of the space for the third ventricle of the brain (obi optic’). If this be right, then fishes have no corpus callosum, unless a transverse communication between these lobes, which some writers regard as such, deserves that appel- lation. As little is there a pons Varolit on the inferior surface in front of the medulla oblongata. In addition to these two negative characters of the brain of fishes, the small development of the cerebrum (anterior brain) in comparison with that of the optic lobes, may be assigned as distinguishing the brain of fishes from that of reptiles and birds. Those parts of the brain, which in man are covered above by the hemispheres of the brain, are here placed behind one another as middle and posterior brains’. The spinal nerves arise, as in the rest of the vertebrate animals, by two roots, one from the posterior or upper, and one from the infe- rior strand of the spinal cord. The posterior roots of these nerves, which swell into a ganglion, are the sentient roots, the anterior the motor roots*. As to the cerebral nerves, the common type of the vertebrate animals prevails in fishes also, and, with the excep- tion of the nervus hypoglossus and accessorius Willisii, all the pairs of nerves that spring from the human brain, occur in almost all 1 Whenever a glandula pinealis is found, as is the case in some fishes, it is situated behind the anterior and in front of the middle lobes of the brain, and thus affords an additional proof that the middle lobes of the brain do not correspond to the cerebrum. See, on the brain of fishes, Hatter Elem. Physiol. tv. 1766, pp. 591—s596; and more fully in Verhandelingen van die Hollandsche Maatschappij der Wentensch. Haarlem, x. 2, pp. 314-386; A. Arsaxy Dissert. de pisciwm cerebro et medulla spinali. Hale, 1813 (new edition by Minter, Leipzig, 1836, 4t0); Cuvier Hist. nat. des Poiss. t. pp. 415—434; C. M. Gorrscuy Vergleichende Anatomie des Gehirns der Griitenfische, MUELLER’s Archiv, 1835, 8. 244—294, 433—486, Taf. Iv. vi. Respecting the reduc- tion of the brain of fishes to the common typus, the most important questions are investigated by MuzLuEr Physiologie, 1. (third edition, 1838, s. 824—829). ? We presume that this physiological truth, of which the discovery is due to C, Butt, is known to the reader; it applies to all vertebrate animals, and is to be regarded, especially since MUELLER’s experiments on frogs (Physiologie, 1. 3tte Auflage, s. 631— 653), as a well established general proposition in our still limited knowledge of nervous function. FISHES. 45 fishes}. The fifth and the tenth pairs of nerves (the nervus tri- geminus and n. vagus) are remarkably developed. The facial nerve, which by many writers is denied to fishes, appears to be represented in bony fishes by the opercular branch of the fifth pair. Of the three pairs of nerves of special sense that for the eyes is the most developed in the greatest number of fishes. The optic nerves arise from the hollow lobes that compose the middle brain, and are at their origin connected by transverse bundles. In the Plagio- stomes there is a chiasma or crossing of the fibres, but in the bony fishes the two nerves themselves le crosswise upon one another ; so that the nerve which springs from the right side runs to the left eye, and that from the left side to the right eye. Here, where the nerves cross one another, they are not connected by any nervous tissue, so that they may be separated and thrown apart without artificial division. The olfactory nerve, when there is no ganglionic swelling in front of the hemisphere of the cerebrum, has such a swelling at its extremity, immediately before it enters the olfactory organ, as in Gadus, Silurus, most Cyprini, and the Plagiostomes. The auditory nerve arises, close to the fifth pair, from the medulla oblongata. The n. vagus arises by two roots from the medulla oblon- gata ; the posterior root is the most conspicuous, and the medulla ob- longata sometimes presents here a considerable swelling (lobus nervi vagt) as in Cyprinus. ‘This nerve mostly surpasses the trigeminus in thickness ; its branches run especially to the branchial arches, but besides this to the cesophagus, the stomach, the heart, the swim- ming-bladder, and in Torpedo and Malapterurus electricus to the electric organ. Moreover from the n. vagus a nerve arises, which runs longitudinally amongst the large lateral muscles, sometimes deeper, in other instances immediately beneath the skin, and which, in those fishes where it lies deeper, gives off a superficial branch which runs longitudinally under the linea lateralis. This nervus 1 In the Myxinoide the nerves of motion of the eye are wanting, according to Muvetier. Compare also on the peripheral nervous system of fishes, besides the works already cited, especially BuEcCHNER Mémoire sur le syst. nerveux du Barbeau, Mémoires de la Soc. d@Hist. nat. de Strasbourg, i. 1835, and H. Srannius Das peripherische Nervensystem der Fische. Mit 5 Steintafeln. Rostock, 1849, 4to. 2 See a figure of it, given by E. H. Wexer, in MecKeEL’s Archiv, 1827, Tab. 1v. fig. 26. 46 CLASS XIV. lateralis cannot be a nerve of motion’; its branches, even when it is situated more deeply, go to the skin. The sympathetic nerve is not present in the Cyclostomes, its place being supplied apparently by the n. vagus. In the Plagio- stomes the cephalic portion is wanting; in the bony fishes this por- tion is situated on the owts¢de of the cranium between the nervus trigeminus, glossopharyngeus and vagus on each side, where it forms three ganglia situated behind one another, which are con- nected by a string running longitudinally, a continuation of the sympathetic nerve of the trunk. Mostly the two sympathetic nerves are united by a transverse branch beneath the bodies of the anterior vertebre. ‘There are two nervi splanchnict, usually one on each side ; in different fishes the two arise from one ganglion on the right side, and are then only very rarely united at their origin into one stem’. The sense of touch is little developed in fishes. Proper organs of tact, like our fingers, by which the form of objects may be investi- gated, are wanting, although the lips perhaps may partly serve for tact. Often there are soft conical appendages or filaments at the lips or jaws which, like the whiskers of mammals, serve for the investigation of external obstacles, and put fishes in a condition to avoid them. ‘The entire skin is little adapted to convey a fine sense of touch; it is the seat of a mucous secretion often largely developed, and is usually covered with scales (see above p. 11). The scales present many striz parallel to the edge, and thus appear to be formed, like the shells of bivalve molluscs, of superposed laminee, as LEEUWENHOECK supposed. Later observers, however, have opposed this laminated origin of scales as horny plates. ‘The scales are not situated in the epidermis alone, but really in the skin, and are included by it; on a fibrous layer formed of connective tissue there lies a layer of pigment, which is covered by an epidermis 1 As little is the ramus lateralis n. trigemini, less usual in fishes, a motor nerve; it arises as a branch which mounts upwards to the cranium, mostly joined by a branch from the n. vagus, and afterwards continues its course along the whole of the back (beneath the dorsal fin). This nerve receives a small branch from all the spinal nerves. 2 Compare on the nervus sympathicus of fishes E. H. WEBER Anatomia compar. nervi sympathici. Lipsiz, 1817, 8vo, pp. 35—66; C. M. Giitay Diss. inaug. de nervo sympathico. L.B. 1834, 8vo, pp. 41-—74; and Sranntus Das peripherische Nervensystem, 8. TZI—143. FISHES. AT formed of flat cells (pavement-epithelium). The scales contain a considerable quantity of phosphate of lime (in well-dried scales it often forms forty per cent. of their weight), and a much smaller quantity of carbonate of lime}. Taste in fishes appears to be very small. The part named tongue in fishes consists merely of the anterior extremity of the tongue-bone covered by mucous membrane. Besides, this part is often armed with teeth, and possesses no proper muscles, so that it is moved in conjunction with the branchial arches alone. The elosso-pharyngeal nerve supplies it with no branches, but is distri- buted chiefly to the first branchial arch, although another branch, usually smaller, is spread upon the palate. If fishes possess the sense of taste, the palate, rather than the tongue, would appear to be its seat. The organ of smell is commonly placed in front of the eyes on each side, on the upper surface of the head; in the Cyclostomes and Amphioxus alone it is single or unpaired. In Lophius piscatorius the organs of smell appear as two small cups attached by a pedicle to the upper lip. The interior of their cavity is covered by mucous membrane, with folds at the bottom which radiate from a centre, or which form transverse strie proceeding on each side from a middle axis. In the osseous fishes each nasal cavity has usually two aper- tures, one in front and one behind. Except in the Myainoids the cavity of the nose has no communication with that of the mouth, as is the case in vertebrates that breathe by lungs. The eyes of fishes, the soles (the genus Pleuronectes) excepted, are situated on each side of the head, often more above, sometimes quite at the side, as in the hammer-fishes (Zygaenw). The bony orbit is not perfectly closed, but open forwards and backwards. The eye-ball is commonly flatter in front and irregularly convex behind. Although capable of little motion, it has still six muscles in most fishes, four straight and two oblique, as in man. In some fishes the 1 Compare on the structure of fishes’ scales AGASsIz (Poiss. foss.), MANDI (Ann. des Se. nat. 2e Série, Tom. x1. 1839, p. 347, and the objections of AGassiz ibid. Tom. XIv. 1840, pp. 98 and foll.), and Peters in MurELuEr’s Archiv, 1841, Jahresbericht, s. 209—216. In the Ganoids, where the scales are covered by an enamel, microscopic investigation indicates bone-corpuscles (/acune), like those which occur in bone. See WILLIAMSON On the microscop. struct. of the scales and dermal teeth of some ganoid and placoid fishes, Phil. Tr. 1849, pp. 435—475, with plates. 48 CLASS XIV. eye-ball, which in such cases is small, is covered by a production of the skin neither attenuated nor transparent: in the most the skin forms round the anterior margin of the eye-ball a circular fold, and then becoming thin and transparent passes over it as conjunctiva. Only few have eye-lids with free edges; some sharks have also a third eye-lid, the membrana nictitans. Lachrymal glands are want- ing. The external coat (sclerotica) is elastic and fibrous; it has on the inside a cartilaginous layer, which sometimes partially ossifies. The cornea is flat, or at least not very convex. On the inside next the sclerotica is situated the external lamina of the vascular coat (choroidea), a glistering silvery or gold-coloured membrane, which passes into the iris; to it succeeds the vascular layer, formed of a network of blood-vessels and covered by a layer of black pigment; this last passes at the posterior surface of the iris into the wea. At the entrance of the optic nerve into the eye-ball is situated in most osseous fishes a vascular body, which surrounds the nerve like an incomplete ring (glandula choroitdalis, comp. above, p. 34). The place where the optic nerve enters the eye-ball is frequently not in the axis of the eye. The retina arises from a streak or irregular white spot, where the optic nerve, mostly in form of a folded band, is expanded. In many osseous fishes a production of the choroidea as a sickle-shaped band (processus falciformis) penetrates the vitreous humour, opposite the entrance of the optic nerve, and attaches itself to the margin of the capsule of the crystalline lens ; generally the attachment is effected by means of a transparent but- ton (campanula Haller’), of which the structure is not yet suffi- ciently known. The vitreous humour is more fluid than in the rest of the vertebrates. The crystalline lens is almost spherical and very large; it projects through the pupil at its anterior part. The aqueous humour is present in small quantity alone’. The auditory organ of fishes consists exclusively of that part which in the higher vertebrate animals constitutes the labyrinth. The external auditory passage, the cavity of the tympanum, the Eustachian tube and the ossicles of the ear are wanting. The 1 Compare RosEnTHAL Zergliederung des Pischauges in Retw’s Archiv, X. 8. 393— 414; D. W. Samuerrine De Oculorum hominis animaliwmque sectione horizontali. Gottingze, 1818, fol. pp. 62—71; GorrscHe Veber die Retina im Auge der Griitenfische, MUELLER’S Archiv, 1834, I. s. 457—466. FISHES. 49 membranous labyrinth in the bony fishes and sturgeons lies for the most part free in the cavity of the cranium at the side of the brain, and surrounded by the same fatty substance ; in the Plagio- stomes and Cyclostomes the auditory apparatus is situated on each side of the cranium in a special cavity, and is included in a carti- laginous labyrinth. In almost all fishes three very large sem- circular canals are present, of which the two perpendicular (the anterior and the posterior eanal) have the part between the two in common, and thus together open into the vestibule by three apertures, whilst the outermost, horizontal canal, opens into it by two apertures. This vestibule (vestibulum, alveus communis) 1s situated below the semicircular canals, and has an elongated sac as an appendage, which is separated from it by a constriction. The posterior part of this sac has a small vesicular appendage (cysticula Brescuet), whilst at the anterior part of the alveus communis there is also a small expansion (wtriculus, appendix clavata vestibul’). In each of these three parts there lies a small stone, of which that which lies in the anterior part of the sac is the largest. These ossicles are hard in the bony fishes, generally grooved, crimped at the margin and sometimes very glistering and of a pure white; in the Plagiostomes and sturgeons they are softer and granular; they consist of carbonate of lime’. In the Cyclostomes neither the stones nor any such sand has been met with. In these the auditory apparatus is also more simple. In Petromyzon and Ammoceetes two semicircular canals alone are found. They are short and thick, and le towards the mem- branous vestibule, into which they open, as well by their broad extremities (the two ampulle), as also by a common aperture at the part where they unite. In Myxine and Bdellostoma MUELL. the entire membranous labyrinth is a single circular canal, which may be regarded in part as a canalis semicircularis, in part as vestibulum. In the Plagiostomes the cartilagmous labyrinth is prolonged beneath the skin and extends to the upper part of the cranium; in the rays also the membranous labyrinth is pro- longed upon the cranium and leads to a membranous sac, which, situated between the cranium and the skin, opens on the skin by one or by three small apertures. These parts are filled with 1 Compare E. Krizcer De Otolithis, Dissert. inaug. physiol. Berolini, 1840, 4to. VOL. II. + 50 CLASS XIV. a calcareous matter. In some bony fishes the labyrinth is extended by a production which unites with that of the opposite side (sinus impar), and afterwards, on the outside of the occiput on each side, terminates in an atriwm on the first vertebra. Here, by means of a chain of small bones, it is brought in connexion with the swimming-bladder’, so that by this the intensity of the vibrations of sound may be augmented. In other osseous fishes the swimming- bladder extends, without such a chain of bones, to membranous spaces in the cranium which are in connexion with the auditory apparatus”. The muscles of fishes consist of loosely united fibres, generally white. On each side of the trunk a large muscular mass is situated, which extends from the head and the osseous belt of the pectoral fins to the base of the caudal fin, on the rays of which it terminates by tendinous bands. This muscular mass is divided by tendinous strips (ligamenta intermuscularia), as though by ribs, into segments lying behind one another; the margins of these strips appear on the surface under the skin as zigzag tendimous incisures (inscriptiones tendinee) descending from the back to the abdomen. This muscular mass is the lateral layer of the trunk-muscles, of which in man the dorsal portion alone is present, and has been developed to form the different muscles of the back. In fishes, on the contrary, it extends over the abdomen. Where ventral fins exist, the two lateral muscular masses separate from each other to leave a fissure in which these fins are received; the pectoral ‘ 1 These bones were named by E. H. WEBER, to whom we owe their discovery, Ge- hirknochelchen, ossicula auditus. GEOFFROY DE St. H1natre, J. F, MecKEL and SAac- MANS MULDER refer them to the first vertebra; the largest, ensiform, hindmost bone, which is immediately connected with the swimming-bladder, would seem to be the rib of the second vertebra. See in detail the investigations of the author last named in Biydragen tot de Natwurk. Wetensch. v1. 1831, bl. 84—105. According to OWEN these bones, with the bony labyrinth, belong to the splanchnic skeleton. Lectwres, 11. p. 210. 2 The first good description of the auditory organ of fishes was given by P. CAMPER Verhandelingen van de Holl. Maatsch. der Wetensch. te Haarlem, vit. t, bl. 79—117, with figs. 1763. Great in this respect are the deserts of Monro and Scarpa. This subject has been treated with great completeness and detail by E. H. WEBER, in his work De Aure et Auditu hominis et animalium. Cum tab. x. Lipsiz, 1820, 4to. Comp. also G. Brescuer Recherches anatom. et physiol. sur Vv Organe deVouie des Poissons, avec 17 Planches. Paris, 1838, 4to, and J. Murtier Ueber den eigenthiimlichen Baw des Gehirorganes bei den Cyclostomen. Berlin, 1838. Mit 3 Kupfertafeln fol. (printed separately from the Abhandl. der Akad. der Wissensch. zu Berlin, aus dem-Jahre 1837). FISHES. Syl fins, situated more on the side, with their muscles pass through a fissure in the anterior part of each of the lateral muscles, which here divide into two bundles. By means of the lateral muscles the spinal column is bent to the right or the left. The principal means of progression for the fish consist in the lateral flexures, the alternate relaxations and curvatures of the tail, or, in the case of cylindrical fishes, as the eel, of the entire trunk’. The surface which reacts upon the water may be greater or less in proportion as the vertical fins (the dorsal, anal and caudal fins), of which the rays are capable of separation from each other and of erection, are more or less expanded. ‘This is effected by muscles, two in number on each side of the interspinal bones: one in front and one behind the projecting line seen on each side of these bones. That in front moves the ray forward and thus extends the fin; that behind draws the ray towards the back, or in the case of the anal fin towards the belly, and thus depresses the fin. Above these muscles there is situated on each side of every ray a superficial muscle inserted into the skin; these last, of which the fibres have an oblique direc- tion as regards the large lateral muscles, move the fins laterally. The ventral and pectoral fins act as oars, and serve the fish principally in directing its course and securing its position in the water. In some fishes the pectoral fins are large enough to be able to support the body in the air for a certain time (flying fishes, Exocetus, Dactylopterus). Vhe pectoral fins can be moved from or towards the body, can be expanded and moved up or down. The forward and backward motion is dependent on the osseous belt to which these fins are attached, and is very limited. These fins are moved by muscles which are attached to the inner and outer surface and inserted into the rays. Those of the inner surface draw the pectoral fins nearer to the body (muscul’ adductores), those of the outer surface move them from it (musculi abductores). The ventral fins can draw their rays together or render them more remote from each other, can move themselves perpendicularly downwards or horizontally outwards and inwards. The head is very slightly, if at all, moveable on the trunk; the jaws, the palatine arch, the tongue-bone, the branchial arches, on the 1S. J. Bruemans pointed out that the stream of water issuing from the gill- aperture on expiration, also assists the progressive motion of fishes. Verhandel. der eerste Klasse van het Hollandsche Instituut, 1. bl. 185—217. Amsterd, 1812. 4—2 52 CLASS XIV. other hand, have great capacity of motion. The principal muscles, which widen the cavity of the mouth and move the gill-covers, are attached to the inner and outer surface of the arch of the palate and to the bones which connect the lower jaw with the cranium. The restorative power of fishes is limited to the reproduction of the parts of fins which have been removed. Many fishes may attain a great age; carps and pikes have been recorded to have lived more than a century. In general they seek their food, especially marine fishes, by night, and then are most easily captured; perhaps they sleep in the day-time. Many fishes pro- bably are torpid during winter. Of the instinct of fishes littleis known. The principal inclination of the fish is the hunting for food, and most of them feed on living prey. For stupifying it some have the power of giving electric shocks. The most remarkable example of art-instinct in the over- powering of prey, is afforded by an East Indian fresh-water fish (Toaxotes jaculdtor), which squirts drops of water upon insects on water-plants in its neighbourhood, to cause them to fall ito the water. The instinct which is directed to the preservation of the species, propagation, offers less that is remarkable in this class than in that of insects and birds, although some species are known that prepare a kind of nest under the water for their offspring’. Many fishes change their abode at certain seasons of the year. Thus, for example, some fishes in spring or summer ascend the mouths of rivers to cast their spawn, as the shad (Clupea alosa); salmons ascend even far inland against the stream of rivers. Some would seem to undertake expeditions annually in countless shoals, as the herrings, which, according to GILPIN, describe in the northern ocean a circuit returning into itself, so that in January and February they appear off Georgia and Carolina, in April off New York, and there in the rivers and bays deposit their spawn, then return to the sea and move towards Newfoundland. Afterwards 1 To these belongs the guxis of ARISTOTELES, a marine fish, that makes a nest of leaves (alge), Hist. Anim. I. vut. cap. 30 (according to CuviER a Gobius), Hist. nat. des Poiss. x11. p. 7, the Doras Hancockii, Cuv. and Vat., according to the observations of Hancock ; to these, finally, also different species of fresh-water sticklebacks belong, Gasterosteus, where the males build the nests, according to the observations of CosTE, lately published. Compare Dict. universal d’ Hist. nat. vit. 1847, pp. 650, 651, Poissons, Pl. 20. : FISHES. 53 they run north-eastwards to the Orkney Islands, where they are found in June, divide at the British Isles about August, and again unite to run towards the south-west im October and November, whilst in December they are found at some distance from the west coast of America, in about 18° or 20° N.L. Then they return northwards to Georgia, &c.* These results, indeed, are founded upon the supposition that the herring of the east coast of North America belongs to the same species with that of the North Sea, which, however, has been since found not to be the case?. On the whole there still prevails much uncertainty respecting the migration of fishes. Most of them do not migrate, or their expeditions are rather to be compared with those of birds of passage, which, without any determinate course, betake them- selves now and then from one place to another. Those marine fishes, which may really be named fishes of passage, change in the northern hemisphere the northern for more southern regions in the spring of the year, whilst birds of passage do the same in the autumn. The cause, therefore, of the passage of fishes must be different from that of birds®. Some species of fishes can exist for a longer or shorter period on dry land, as the common eels. Different species of Callichthys and Doras bury themselves in the mud when the ponds in which they live become dry, or even creep, as HANCOCK witnessed in a species of Doras, over the ground, sometimes in large troops to another pond. The sand-eel (Ammodotes tobianus) lives in the sand and especially m the clayey bottom of the sea, in which it buries itself deep and through which it winds in all directions; it some- times approaches so close to the shore that it may be dug out at 1 Observations on the annual Passage of Herrings, Transact. of the Americ. Philos. Soc. Vol. 11. Philadelphia, 1786, pp. 236—z39. 2 The herring of New York is Clupea elongata LESUEUR. See Cuv. et VAL., Hist. nat. des Poiss. XX. p. 247. [‘There can be no doubt that the herring inhabits deep water all round our coast, and only approaches the shores for the purpose of depositing its spawn.” YARRELL British Fishes, 1. p. 112; see the paper of M¢CuLLocH quoted by YARRELL in Journ. of Roy. Institution, Jan. 1824.] 3 A prize essay of Marcen Dx Serres on the History of Fishes of Passage (Natuurk. Verhandelingen van de Holl, Maatschappij der Wetenschappen te Haarlem, te Verzam. 2e Deel. 1842, 4t0) throws little light on this matter, and may be regarded asa failure. 54 CLASS XIV. ebb-tide with a spade, as in some parts of Zealand’. Salarias alticus climbs over the rocks by the aid of its fins, and leaps four or five feet when attempted to be taken. That many fishes, swimming on the surface of the water, often make short leaps into - the air, is known to all: the flying fishes (xocetus), noticed above, can leap full twenty feet whilst flapping with their large pectoral fins. Fishes, in respect of their residence, may be divided mto such as inhabit the sea, and others fresh-water, although some, as we have lately said, migrate from the sea to rivers and from these to the sea. The number of species that dwell in the sea is, how- ever, much larger than those in fresh water, and is to the last probably as 3:1. Most of the fresh-water fishes are found amongst the soft-finned (Malacopterygi) in the families of the Salmonacet, Stluroided and Cyprinoidei, of which the last is especially abundant in species; amongst the Acanthopterygi the number of fresh-water species may be stated as certainly less than the thirtieth part of all the known species. On the whole the physical distribution of fishes is bounded by narrower limits than that of the other animal species. As a rule, no fishes are found in hot springs, in which many other animals frequently live, although a species of Cyprinus (Leuciscus thermalis) has been found in the Tsland of Ceylon in a hot spring of 50° centigr. On high mountain levels, where there is often a luxuriant vegetable growth, and where many birds and insects live, only a few fishes are found in the rivers and ponds, as the Hremophilus Mutisti in the river Bogota, 8000 feet above the level of the sea. In the brooks on the highest Altaic mountains no fishes are found. Some fishes live in sub- terranean lakes. The geographic distribution of fishes indicates some general results which agree with those presented by molluscs (see above, 1 The Dutch reader will here recall probably the well-known romance of BELLAMY, and the lines: Dan gaat de jeugd met spade en ploeg Naar’t breede vlakke strand, &e. Anabas (Perca scandens), an Indian fresh-water fish, not only quits the water, accord- ing to DaLporr and Joun, but even climbs the palms upon the bank, by aid of the spines on its gill-covers. Other writers, however, and especially HAMILTON BUCHANAN, contradict these statements. FISHES. 30 Vol.1. p. 770). There are few species alone which may be regarded as cosmopolitan, and then only in an improper sense, whilst they occur, for example, in most seas only, but not in the North Sea, as Temnodon saltator. ‘The fishes of the Mediterranean are met with in part in the North Sea also; but many are peculiar to this large lake, or spread themselves along the west-coast of North Africa to the Atlantic Ocean. The Red Sea is in many respects to be regarded simply as a part of the Indian Ocean, and contains many genera which do not occur in the Mediterranean, and even many species which extend themselves to the extreme limits of the Indian Archipelago, and sometimes even to the Southern Pacific. Amongst the fresh-water fishes, the numerous genus Cyprinus Li. especially, and the allied genus Coditis, are to be regarded as a group of the Hastern hemisphere, of which the greatest number of species occur in India, whilst only a few are met with in North America and none in South America. On the other hand, the Stlwroids occur equally in both hemispheres of the earth, although many forms are found in the Western hemi- sphere alone. The use which man derives from the fishes is very great. Many races of people live exclusively or principally on fish. Salted or dried, and thus rendered fit for transmission to a distance, they form an important branch of commerce for seafaring nations ; they afford us train oil, isinglass, &c. The number of fishes of which the use is injurious, is only small when compared with that of the edible and useful. The arrangement of fishes is attended with great difficulties, and it seems to be rather the avoidance of what is frail than the attainment of what is perfect, that the most earnest investigations and the most learned disquisitions have yet to offer us. SYSTEMATIC ARRANGEMENT OF FISHES. CLASS XIV. FISHES. VERTEBRATE animals breathing during the whole life by per- sistent branchiea, having cald blood and a ventricle of the heart single, branchial alone ; aquatic, mostly oviparous. I. Organ of smell unpaired. Section I. Dermopterygit. Fins surrounding the body at the back and abdomen with a cutaneous border: pectoral and anal fins none. Dorsal cord per- sistent, in place of a vertebral column. (Swimming-bladder none. Ribs none.) Body covered by a soft skin, not scaly. OrverR I. Leptocardii. Pulsating vessels in place of heart. Blood pale. Branchial sac in front of cesophagus, included in the cavity of body. Family I. Amphiowint. (Characters of the order those of the single family.) Body compressed. Amphioxus Y ARRELL (Branchiostoma Costa). Body acuminate at both ends; dorsal fin extended at the back through the whole length, confluent at the tail with the anal. Mouth inferior, pre- senting a longitudinal fissure, furnished with somewhat rigid cirri (12—15 on each side). This genus of fishes is the most imperfect of the typus of verte- brate animals. There is no brain present, at least not as -a distinct PISCES. 57 organ; this part of the central nervous system is represented by the anterior obtuse extremity of the spinal cord. The chorda dorsalis, terminating in a point at both ends, has two sheaths, from the most external of which a fibrous lamina is extended upwards on each side ; these two laminz approach each other and finally coalesce. In this way a canal is formed above the chorda dorsalis in which the spinal marrow is contained. But the entire canal is not filled by this: it is divided by a thin transverse partition into a larger inferior portion inclosing the spinal cord, and a smaller upper portion containing a cellular tissue saturated with fat. Above this last portion the two laminz unite to form a crest on which the rays of the dorsal fin rest. The mouth is surrounded by two strips of cartilage, consisting of jointed pieces, each of which terminates laterally in a conical point ; these points are the supports of the cirri that surround the mouth. Behind the mouth commences the branchial cavity, which is supported by numerous cartilaginous strips and invested by a mucous membrane covered with vibratile cilia ; small fissures are left between the strips of cartilage, which do not open on the skin but terminate in the cavity of the body. In front of the anus is an aperture (porus abdominalis) by which the water escapes, and which may therefore be regarded as a respiratory aperture, but through it the eggs and the sperma are also evacuated. The intestinal canal, as in the Ascidie (of the branchial sac of which Amphioxus reminds us), commences at the bottom of the branchial cavity, and has a lateral expansion of a green colour terminating in a blind extremity forwards, which probably corresponds to the liver. The intestinal canal throughout its entire extent is beset with vibratile cilia ; it has no convolutions, and becomes narrower below ; the anus is situated at a short dis- tance from the extremity of the body, somewhat to the left side. The sexual organs are in both sexes of the same structure, and form on each side of the abdominal cavity a series of irregular four- sided organs, which extends to the porus abdominalis, and are visible through the skin. On the under surface, on each side, a fold of skin has been observed, extending to the porus abdominalis, in which a canal is situated terminating close to this last behind and in front in the mouth. We give the preference to the name Amphioxus, although devised a couple of years later than that of Branchiostoma for this genus of animals, since the last is less commonly known, and moreover originated in the mistake that the oral cirri are gills. 58 CLASS XIV. Compare on this genus: W. YARRELL History of British Fishes, 1. 1836, pp. 468—472. H. RatuKxe Bemerkungen tiber den Bau des Amphioxus lanceolatus. Mit einer Kupfertafel. Konigsberg, 1841. J. Murtier Veber den Bau u. die Lebenserscheinungen des Branchao- stoma lubricwm Costa. Mit 5 Kupfert. Berlin, 1844, 8vo. A. De QuatrEeFacEes Mémoire sur le syst?me nerveux et sur Vhistologie du Branchiostome ou Amphioxus, Ann. des Sc. nat. 3¢ Série, Tom. Iv. Zool. 1845, pp. 197—248, Pl. 1o—13. The descriptions of the Neapolitan naturalist Costa (Cenni Zoologici, 1834, Fauna del Regno di Napoli, 1839), are known to me from citations alone. Also of the paper of J. GoopsiR, Trans. of the roy. Soc. of Edinburgh, xv. 1841, I have only been able to consult the short account in the Ann. of nat. Hist. vil. pp. 346—348. Sp. Amphioxus lanceolatus YARRELL, Branchiostoma lubricum. This species, the only one as it seems of this genus, occurs in different seas, and nume- rously in some places in the Mediterranean; it buries itself in the sand of the shore; its length is from 1} to 2”. Pawas, who first described and figured it, held it to be a mollusc, whence he named it Limazx lanceolatus. Spicileg. Zoolog. Fasc. X. Tab, I. fig. 11. OrveER II. Cyclostomi. Blood red. Heart distinct. Branchial artery without bulb, furnished at the base with two valves. Body cylindrical. Branchiz furnished with external spiracles, sacciform, six or seven on each side. Family Il. Myxinoidet (Hyperotreta MuEtt.). Body cylin- drical, obliquely truncated anteriorly. Mouth anterior, cirrose ; olfactory cavity furnished anteriorly with a tracheal tube leading to an external aperture above the mouth, posteriorly with a canal perforating the palate. Single horny tooth in palate; smaller teeth in a double row on each side in tongue, recurved. Branchie on each side with internal ducts leading to the cesophagus. The work of J. Murtter, already cited, Vergleichende Anatomie der Myxinoiden, Abhand. der Koenigl. Akademie der Wissenschaften zu Berlin, 1834, 1838, 1839, 1842, has, in particular, greatly illustrated this family. The perforated palate, the connexion of the cavities of the nose and the mouth, is not found in other fishes, and is besides a common character of vertebrates that breathe by lungs. The inferior margin of the mouth, since no under-jaw is present, is formed by the anterior extremity of the tongue-bone. PISCES. 59 Myzxine Li. Two spiracles approximate on the ventral surface behind the branchiz, each spiracle receiving the external ducts of the six branchiz of its own side. Eyes very small, hidden by muscles. Sp. Myzxine glutinosa L., Gastrobranchus cecus Buocs, Linn. Mus. Ad. Fred. Tab. vit. fig. 4, Buocn Syst, Ichth. Tab. 104; Cuvier R. Ani., éd. ill., Poiss. Pl. 120, fig. 3; lives in the North Sea. Linyaus referred it to the worms, regarding the two lateral parts of the tongue as transverse jaws (maxille transversales), which do not occur in vertebrate animals. There is a duet which leads immediately from the cesophagus to the left spiraculum ; a similar duct occurs also in the following genus, going to the posterior spiraculum branchiale of the left side. The animal is about 11” long. Bdellostoma Muvrtu., Heptatrema Dumix. Branchiz on each side six or seven, each supplied with an external spiracle. Eyes small, conspicuous through the skin. Fishes from the southern seas, for which the name Heptatrema can scarcely be retained, since individuals are met with having six gill-apertures on each side, or six on the right side and seven on the left ; the species are not yet sufficiently defined; they closely resemble Myaine glutinosa in internal structure, notwithstanding the external characters ; frequently, how- ever, they attain a larger size. There are seven gill-apertures on each side in Petromyzon cirratus, Bdellostoma Forsteri MUELL. ; see Buocu Syst. Ichth. pp. 531, 533. To this genus belongs a species imperfectly described and badly figured by LacrrEpE Gastrobranchus Dombey ; Poiss. 1. Pl. 23, fig.1. Family UI. Petromyzonini (LHyperoartia): Body cylindrical, with mouth anterior, lip circular or lunate. Olfactory cavity open above by an external nasal foramen, produced posteriorly into a blind canal, not perforating the palate. Thorax cartilaginous, sus- taining the branchial apparatus, composed of strips descending on each side beneath the skin from the back towards the ventral sur- face. Two dorsal fins, the posterior conjoined with the caudal fin. Petromyzon L. (exclusive of Petr. branchialis). Several labial and lingual teeth. Branchiz open internally in a subcesophagean tube, blind posteriorly, Labial ring circular, margined by many small cirri. Sp. Petromyzon marinus L., Buocu Ichth. Tab. 77, GusRin Iconogr., Poiss. Pl. 70, fig. 1, YARRELL Brit. Fishes, 1. p. 448 ; Petromyzon fluviatilis L., Buiocw Ichth. Tab. 78, fig. 1, Cuv. R. Ani., éd. ill., Poiss, Pl. 120, fig. 1 (named Petr. marin.). The first of these species, the marine, comes on the approach of summer into rivers, and attains a length of more than two feet ; the last, much smaller, appears to live constantly in fresh water. This species is named Lamprey (Lampetra from lambendo petras), Pricke, &c. These animals use their tongue as a sucker, and attach themselves to different bodies ; they then inspire and expire by the external branchial & 60 CLASS XIV. apertures, On the anatomy, the memoir of H. Raruxe (Bemerkungen tiber den innern Bau der Pricke, Petromyzon fluviatilis. Dantzig, 1825, 4to) may be regarded as the chief work. The Dutch Society of Sciences has published a valuable memoir of Prof. Max ScuutrzEe of Halle, Die Lntwickelungsgesch. von Petromyzon Planeri. Mit vit. Taf. (Watuurkundige Verhandelingen van de Hollandsche Maatschappij der Wettensch. te Haarlem. Tweede Versameling, Deel xt1, 1856, 4to.) The cleavage of the yolk is entire, and in the first stages of development there is much analogy with that of the frog. Ammocetes DuméR. Teeth none. Branchie open internally in the pharynx. External branchial apertures small, placed in a longi- tudinal furrow. Upper lip semicircular. Comp. Dumérin Dissertation sur les Poissons cyclostomes (Magasin ency- clopédique, 1808); RatHke Beitriige zur Gesch. der Thierwelt, 1V. 1827, 8. 66—102, Tab. II. IIT. Sp. Ammocetes branchialis, Petromyzon branchialis L., Gu&R1In Iconogr., Poiss. Pl. 70, fig. 3, YARRELL Brit. Fishes, 1. p. 459. In fresh water in many countries of Europe, keeping mostly at the bottom or in the sand ; this species attains a length of 6 or 7”. Avuc. Murnier (Ueber die Entwickelung der Newnaugen, MUELLER’S Archiv, 1856, pp. 323—339) has found that Ammocetes is the larval form of Petromyzon. The perfect state is not attained until the fourth year from the egg. II. Organ of smell double. A. Muscular bulb at the base of branchial artery, with nu- merous valves disposed in longitudinal rows. Section Il. Chondropterygi. Fins supported by cartilaginous rays. Pectoral and ventral fins. Skeleton cartilaginous; cartilaginous arches closed, forming a canal for the spinal cord; bodies of vertebra distinct in most, in some the chorda dorsalis persistent, situated under the arches in- closing the spinal cord, continuous. Tail recurved upwards, with caudal fin inferior. Skin mostly rough with small bony scales, or covered with large dispersed scutes, sometimes naked. Mouth situated under the head. (Ribs distinct in most; swimming-blad- der none.) Orper Til. Desmiobranchii s. Plagiostomi. Branchiz adhering to the skin by their outer margin, patent by lateral external apertures on each side. True operculum none. PISCES. 61 Mouth a transverse fissure on the lower part of the head. Bones of cranium not distinct by sutures. Copulation. Compare J. MuELLER und J. HEnuE Systematische Beschreibung der Plagiostomen. Mit 60 Steindrucktafeln. Berlin, 1841, folio. This order may in many respects be regarded as the most compo- site and the most highly organised in the class of fishes, whence some recent writers place it at the top of the class and far from the Cyclostomes. The conviction that it is an impossibility to preserve the natural affinity, when animals are arranged in a single line, has withheld us from making such a revolution in the previous and more common arrangement of fishes. The cranium of these fishes preseuts no sutures. A single bone attaches the lower jaw to the skull, taking the place of the jugal bone, of the tympanicum, epitympanicum, and preoperculum (see above, pp. 20, 21). At the posterior margin of this bone cartilaginous appendages are attached digitally, which correspond to the opercula of the bony fishes. There are thin cartilaginous strips beneath the skin which support the margins of the external branchial apertures, and replace the more composite apparatus of the Petromyzonines. Hence it is obvious that the apparatus in Petromyzon is not homolo- gous with branchial arches. Above, on the head, with few exceptions, are two apertures behind the eyes, in front of the quadrate or suspensory bone of the lower jaws ; they conduct to the mouth and transmit the water that has been distributed to the gills (foramina temporalia, évents, Spritz-locher). A real copulation occurs in these fishes ; compare above, pp. 39, 40. All have a spiral valve in the intestinal canal. Family IV. atides. Body depressed. Branchial apertures on the neck below, five on each side. Eyelids connate with the eyes or none. Cartilaginous belt sustaining the pectoral fins adher- ing above to the vertebral column. This family consists principally of the genus Raja L., to which, as MueLurr has remarked, Squalus Pristis L. might be added, which forms indeed the transition to the following family, but still agrees with the rays in essential characters: the branchial apertures are situated on the ventral surface, &e. In this family the dorsal fins are commonly far backwards. In some species of rays individuals occur with a membrane on the middle of the disc of the body, as in Raja clavata; such varieties 62 CLASS XIV. have been regarded incorrectly as distinct species. See a figure in LacereDE Poiss. 1. Pl. vir. fig. 1. Many species have spines or tubercles on the back, on the fins and the tail, which vary in number and development according to age and difference of sex. A. Tail slender. Body discoidal, broad. + A serrated spur at the base of tail. Cephaloptera Dumér. (Pterocephala Swatns.). Pectoral fins very broad, acuminate towards the point, produced in front of the head like ears. ‘Teeth small. Sp. Cephaloptera Giorna Risso, Raja giorna Lac., Poiss. v. Pl. 20, fig. 3, GuérRIN Iconogr., Poiss. Pl. 69, fig. 4; attains a breadth of more than 4 feet; this species occurs in the Mediterranean, but species from the East Indies, Japan and Brazil are also known. Ceratoptera Murty. and HENLE. Myliobatis Cuv. Pectoral fins broad, acuminate towards the apex, interrupted at the sides of head, surrounding the head an- teriorly. Teeth large, composed of vertical fibres or cylinders, forming transverse flat laminz, covering each jaw with mosaic work. ‘Tail flagelliform, very long, armed with a serrated spur behind the dorsal fin. Sp. Myliobatis aguila Risso, Raja aguila L., YARRELL Brit. Fishes, 1. p- 445, Mediterranean Sea, ke. Sub-genera: Rhinoptera Kun, Aétobatis MUELL. and HENLE. Sp. Aétobatis flagellum, Raja flagellum. Buocw Syst. Ichth. Tab. 73, habit. in Indian Sea, &c. Trygon ADANS. Pectoral fins surrounding the head and often produced into a point in front of head. Dise of body oval, or- bicular or obtusely rhombic. Teeth placed in alternate rows, rhombic. Tail mostly of length of body, without finlets, furnished with single or double serrate aculeus. Add genera Uvrolophus and Trygonoptera Murti. and HENLE. Anacanthus Enrens.