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[ANATOMY
IGHTHYOLOGY


by the death of the author); E. W. L. Holt, “Recherches sur la reproduction des poissons osseux, principalement dans le golfe de Marseille, ” Ann. Mus. Mars. v. (Marseilles, 1899); (I) WESTERN AND CENTRAL ASIA: L. Lortet, “ Poissons et reptiles du lac de Tibériade, " Arch. Illus. d'Hist. Nat. Lyon, iii. (1883); S. Herzenstein, Wisserlschaftl-iche Resultate der von N. M. Przewalski nach Central Asien unternornmenen Reisen: Fische (St Petersburg, 1888-1891); L. Berg, Fishes of Turkestan (Russian text, St Petersburg, 1905); G. Radde, S. Kamensky and F. F. Kawraisky have worked out the Cyprinids and Salmonids of the Caucasus (Tiflis, 1896-1899). (]) ]APAN: F. Steindachner and L. Doderlem, " Beitrage zur Kenntniss der Fische ]apans,1' Denkschr. Ak. Wien, (vols. 67 and 68, 1883); K. Otaki, T. Fujita and T. Higurashi, Fishes of Japan (in Japanese) (Tokyo, 1903, i1'lEI'Ogl'CSS). Numerous papers by D. S. Jordan, in collaboration wit O. Snyder, E. C. Starks, H. W Fowler and N. S1ntlo. (K) EAST IND1Es: F. Day, The Fauna of British India: Fishes (2 vols., London, 1889) (cliieiiy an abridgment of the author's Fishes of India); M. Weber, ' Die Siisswasserfische des Indischen Archipels, " Zoot. Ergebnisse e. Reise in Niederl. Ostind. iii. (Leiden, 1894). Numerous contributions to the fauna of the Malay Peninsula and Archipelago by G. A. Boulenger, L. Vaillant, F. Steindachner, G, Duncker, W. Volz and C. L. Popta. (L) AFRICA: G. A. Boulenger, Matériaux pour la faune du Congo: poissons nouveaux (Brussels, 1898-1902, in progress); and Poissons du bassin du Conga (Brussels, 1901); G. Pfeffer, Die Thierwelt Ostafrikas: Fische (Berlin, 1896); A. Giinther, G. A. Boulenger, G. Pfeffer, F. Steindachner, D. Vinciguerra, j. Pellegrin and E. Lonnberg have published numerous contributions to the fish-fauna of tro ical Africa in various periodicals. The marine fishes of South Afiiiica have received specia attention on the part of ]. D. F. Gilchrist, Marine Investigations in South Africa, i. and ii. (1898-1904), and new species have been described by G. A. Boulenger and C. T. Regan. (M) NORTH AMERICA! D. S. jordan and B. W. Evermann, The Fishes of North and Middle America (4 vols., Washington, 1896-1900); D. S. jordan and B. W. Evermann, American Food and Game Fishes (New York, 1902); D. S. jordan and C. H. Gilbert “The Fishes of Bering Sea, " in Fur-Seals and Fur-Seal I slancls (Washington, 1899); The U.S. Bureau of Fisheries (since 1903) has published annually a Report and a Bulletin, containing a vast amount of information on North American fishes and every subject having a bearing on the fisheries of the United States; S. E. Meek, “ Fresh-water Fishes of Mexico, " Field Colurnb. Mus. Zoot. v. (1904). (N) SOUTH AMERICA: C. H. and R. S. Eigenmann, “ A Catalogue of the Fresh-water Fishes of South America, " Proc. U.S. Nat. Mus. 14 (Washington, 1891); the same authors, F. Steindachner, G. A. Boulenger, C. Berg and C. T. Regan have published contributions in periodicals on this fauna. (O) Aus-TRALIA: ]. E. Tenison-Woods, Fish and Fisheries of New South Wales (Sydney, 1882); j. Douglas Ogilby, Edible Fishes and Crustoceans of New South Wales (Sydney, 1893); ]. Douglas Ogilby and E. R. Waite are authors of numerous papers on Australian fishes in Proc. Linn. Soc. N.S. Wales and Rec. Austral. Mus. (P) SOUTH PACIFIC: D S. jordan and B. W. Evermann, “ Shore Fishes of the Hawaiian Islands, " Bull. U.S. Fish. Comm. 23 (1905). (Q) MADAGASCAR z H. E. Sauvage, Histoire physigue, naturelle et politique de Jlladagascar, par A. Grandidier. xvl.; oissons (Paris, 1891). (R) OCEANIC Fisuissz G. B. Goode and T. H. Bean, Oceanic Ichthyology (WaShingron, 1895); A- Gunther, Deep-sea Fishes of the “ Challenger " Expedition (London, 1887); C. H. Gilbert, “ Deep-Sea Fishes of the Hawaiian Islands, " Bull. U.S. Fish. Comm. 23 (1905); R. Collett, Norske Nordhaos Expedition: Fiske (Christiania, 1880); C. F. Lutken, Dijmphna-Togtets Zoologisk-botaniske Udbytte: Kara-Haoets Fiske (Copenhagen, 1886); L. Vaillant, Expeditions scienti#ques du “Tra11ailleur” et du “I'alisrna, n”: Poissons (Paris, 1888); A. Agassiz, Three Cruises of the U.S. Coast and Geodetic Survey Steamer “ Blake " (Boston and New York, 1888); A. Alcock, Illustrations of the Zoology of II.M.S. “ Investigator": Fishes (Calcutta, 18192-1899, in progress); -. Alcock, Descriptive Catalogue of the In ian Deep-sea Fishes in the Indian Museum (Calcutta, 1899, contains references to all the previous papers of the author on the subject); R. Collett, Résultats des carnpagnes scientitiques ac complies par Albert I” prince de Monaco: poissons prooenant des camlpagnes du yacht “ l'IIirondelle, " (Monaco, 1896); R. Koehler, Résu tats scienizfiques de la canipagncfdu “ Caudan, " (Paris, 1896); C. H. Gilbert and F. C ramer, “ Re ort on the Fishes dredged in Dee Water near the Hawaiian lslanclh, " Proc. U.S. Nat. Mus. xix. (r)Washingt0n, 1896); C. Liitken, “Spolia Atlantica, " Vidensk. Selsk. Skr. vii. and ix. (Copenhagen, 1892-1898); C. Lutken, Danish Ingolf Expedition, ii.: Ichtlzyological Results (Copenhagen, 1898); S. Garman, “ Reports on an Exploration off the West Coast of Mexico, Central and South America, and off the Galapagos Islands in charge ot AlexanderAgasSiz, by the U.S. Fish Commission Steamer "Albatross, " during 1891, " Mem. Mus. Comp. Zool. vol. xxiv. (Cambridge, U, S.A., 1899). (S) ANTARCTIC FISIIES: G. A. Boulenger, Report on the Collections made during the voyage of the “Southern Cross "I Fishes (London, 1902); L. Dollo, Expédition Antarctigue Belge (S.Y. “ Belgica

). Poissons (Antwerp, 1904); E. Lonnber, Swedish South

Polar Expedition: Fishes (Stockholm, 1905); A. Boulenger, Fishes of the “ Discovery " Antarctic Expedition (London, 1906). (G. A. B.)

III. DEFINITION or THE CLASS Pisces. ITS PRINCIPAL Divisions

Fishes, constituting the class Pisces, may be defined as Craniate Vertebrata, or Chordata, in which the anterior portion of the central nervous system is expanded into a brain surrounded by an unsegmented portion of the axial Skeleton; which are provided with a heart, breathing through gills; and in which the limbs, if present, are in the form of fins, as opposed to the pentadactyle, structure common to the other Vertcbrata. With the exception of a few forms in which lungs are present in addition to the gills, thus enabling the animal to breathe atmospheric air for more or less considerable periods (Dipneusti), all fishes are aquatic throughout their existence.

In addition to the paired limbs, median fins are usually present, consisting of dermal rays borne by endoskcletal supports, which in the more primitive forms are strikingly similar in Structure to the paired fins that are assumed to have arisen from the breaking up of a lateral fold Similar to the vertical folds out of which the dorsal, anal and caudal fins have been evolved. The body is naked, or scaly, or covered with bony Shields or hard spines. Leaving aside the Ostracophori, which are dealt with in a separate article, the fishes may be divided into three subclasses I. Cyclostomi or Marsipobranchii, with the skulldmperfectly developed, without jaws, with a Single nasal aperture, without paired fins, and with an unpaired fin without dermal rays. Lampreys and hag-fishes. f

II. Selachii or Chondropterygii, with the Skull well developed but without membrane bones, with paired nasal apertures, with median and paired fins, the ventrals bearing prehensile organs (claspers) in the males. Sharks, skates and chirnaeras. III. Teleostomi, with the skull well developed and with membrane bones, with paired nasal apertures, primarily with median and paired fins, including all other fishes. (G. A. B.) IV. ANATOMYI, ,

The special importance of a study of the anatomy of fishes lies in the fact that fishes are on the whole undoubtedly the most archaic of existing craniates, and it is therefore to them especially that we must look for evidence as to the evolutionary history of morphological features occurring in the higher groups of vertebrates.

In making a general survey of t'he morphology of fishes it is essential to take into consideration the structure of .the young developing individual (embryology) as well as that of the adult (comparative anatomy in the narrow Sense). Palaeontology is practically dumb excepting as regards external form and skeletal features, and even of these our knowledge must for long be in a hopelessly imperfect state. While it is of the utmost importance to pay due attention to embryological data it is equally important to consider them'c1itically and in conjunction with broad morphological considerations. Taken by themselves they are apt to be extremely misleading.

External Features.-The external features of a typical fish are intimately associated with its mode of life. Its shape is more or less that of a spindle; its 'surface is covered with a highly glandular epidermis, which is constantly producing lubricating mucus through the agency of which Skin-friction is reduced to an extraordinary degree; and finally it possesses a. set of remarkable propelling organs or fins. The exact shape varies greatly from the typical spindle shape with variations in the mode of life; e.g. bottom-living fishes may be much fattened from above downwards as in the rays, or from side to side in the Pleuronectids such as iiounder, plaice or sole, or the shape may be much elongatedias in the eels.,

Head, Trunk and Tail.-In the body of the fish we may recognize the three main Subdivisions of the body-head, trunk and tail-as in the higher vertebrates, but there is no definite narrowing of the anterior region to form a neck such as occurs in the higher groups, though a suspicion of such a narrowing occurs in the young Lepidosiren.

1For general anatomy of fishes, see T. W. Bridge, Cambridge Natural History, and R. Wiedersheim, Vergl. Anat. der Wirbeltiere.

The latter contains an excellent bibliography.