222 



ICHTHYOLOGY. 



Introduc- of progression as those of the other vertebrated classes ; 

 tion. (}jgy sgi2g^ and some divide, their food with their teeth ; 

 ihgestive jj^^y digest it in the stomach, from wlience it passes into the 

 V _", intestinal canal, where it receives a supply of bile from the 



liver, and frequently a liquid similar to that of the pancreas ; 

 the nutritive juices, absorbed by vessels analogous to lacteals, 

 and probably taken up in part also directly by the veins, 

 are mingled with the venous blood which is flowing towards 

 the heart, from whence it is pushed to the branchiae, in 

 which, coming into contact with the water, it is converted 

 into arterial blood, and then proceeds to the nourishment of 

 the whole body. As in other animals, also, certain pro- 

 perties are carried off from the blood by transpiration, the 

 secreting power of the kidneys, &c. 



Fishes in general are extremely voracious, and the nile 

 of "eat or be eaten" applies to them with un\isual force. 

 They are almost constantly engaged in the pursuit and 

 capture of their prey ; their degree of power in these re- 

 spects depending of course on the dimensions of the mouth 

 and tliroat, and the strength of the teeth and jaws. If the 

 teeth are sharp and hooked, they are capable of securing 

 the slenderest and most agile animals ; if they are broad 

 and strong, they are able to bruise the hardest aliment ; if 

 they are feeble or entirely wanting, they are only service- 

 able in procuring some inert or unresisting prey. Fishes 

 indeed show but little choice in the selection of their food, 

 and their digestive powers are so strong and rapid as to 

 suffice to dissolve very speedily all kinds of animal sub- 

 stances. They greedily swallow other fishes, notwithstand- 

 ing the sharp spines or bony ridges with which they may 

 be armed ; they attack and devour crabs and shell-fish, 

 gulping them entire if they cannot otherwise attain their 

 object ; they do not object occasionally to swallow the young 

 even of their own species, and the more powerlul kinds 

 can-y their warfare into other kingdoms of nature, and re- 

 vel on rats, reptiles, and young ducklings, to say nothing of 

 the ferocious Shark, which not seldom makes a meal even 

 of the lord of the creation. The species which live chiefly 

 on vegetable substances are few in number. 



The growth of fishes depends greatly on the nature and 

 supply of food, and different individuals of the same species 

 exhibit a great disparity in their respective dimensions. 

 They grow less rapidly in small ponds or shallow streams, 

 than in large lakes and deep rivers.' The growth itself 

 seems to continue for a great length of time, and we can 

 scarcely set bounds to, certainly we know not with preci- 

 sion, the utmost range of the specific size of fishes. Even 

 among species in no way remarkable for their dimensions, 

 we ever and anon meet with ancient individuals, fiivourably 

 situated, which vastly exceed the ordinary weight and mea- 

 surement of their kind. 



The teeth of fishes are more variable in form, structure, 

 number, and position, than 

 those of any other class of 

 animals. They are depressed 

 prisms of three, four, five, or 

 six sides in Myletes, Mylioha- 

 tes or Scarus. More generally 

 they are round and tapering, 

 varying in length and thick- 

 ness from the " short obtuse 

 cone," to the " long conical," 

 " subulate," " acicular forms," 

 even to such fineness as to be 

 named " ciliiform." 



and bent at right angles, and their bases may be fixed or Introduc- 

 moveable. In some Gobiida their forms and free motion t'oo- 

 have ca\ised them to be compared to the keys of a piano. Digestive 

 When acicular or ciliiform teeth are arranged so closely as to ^ System. ^ 

 resemble the pile of velvet, they are said to be " villiform" ^"^'""'^ 

 {en velours) ; and when coarser and straight, or with their 

 points bent back, they are " card-like," or " cardiform," 

 or they may be rasp-like or carduliform {en rape ou en 

 cardes). The Chatodonlidce are named from their seti- 





% 



Fig. 63. 



Head of Histioptems recurvirostris, one of the Squamipenna or Chcetodon- 

 tidf€. The teeth, as in the true Ch^etodons, are closely set, but they are 

 stouter than the "villiform" teeth, and even than thoso usually named 

 *' setiform," having a resemblance to the cylindrical blunt fibres of whale- 

 bone in a scrubbing-brush, hence they may be termed coarsely "brush- 

 like" (en brasses). They are somewhat thicker than the strong hairs of an 

 elephant. 



form teeth. In the Sphyrana we have examples of teeth 

 exactly resembling the blade of a surgeon's lancet {vide 

 fig. 19), and in Sharks 

 the teeth have a variety 

 of forms, from the long 

 triaedral dagger or spike- 

 nail of Oxyrhina and 

 Odontaspis, to the ser- 

 rated or lobed cutting 

 teeth of Galeocerdo, 

 Carcharodon, Cacharias, 

 and other genera, set in a 

 row so as to make a most 

 powerful instrument, by 

 which one of these crea- 

 tures is able to divide a 

 man's body into two at a ^. ,, 



I , . -^ , , Fig. 54. 



Single bite, down to the Onfices of the mouth and nostrils of fftmj- 

 scyllium trispecttlare. The teeth areseated 

 in the skin covering the cartilages of the 

 jaws, and, as the skin grows outwards 

 (peripheral) like the nails of a man's 

 fangers, the teeth as worn dropotf, or de- 

 squamate, and are succeeded by others 

 from within, gradually rolling over the 

 cartilages. Fig. 11 gives a full-length 

 view of this lish. 



Fig. 52. 

 Petroscirtes Bankterl 



Their points may be curved, reflexed. 



pavement-like or tessel- 

 lated teeth {en paves) of 

 the Dog-fish, or Ces- 

 tracio7i, used for crush- 

 ing. The Carp has a 

 crushing apparatus at the 

 entrance of the gullet. In Myliohates, Aetobates, Hhin- 

 optera, the pavement formed by the broad teeth is of the 

 most regular and beautiful kind. In Scarus and Hopleg- 

 7iathus or Scarodon, the teeth are so united to the pre- 

 maxillaries and mandible as to form but a single tooth 

 in each jaw, while in Calliodon, the union of the teeth 



• The writer of this treatise kept a minnow little more than half an inch long in a glass tumbler for a period of two years, during 

 which time there was no perceptible increase in its dimensions. Had it continued in its native stream, subjected to the fattening 

 influence of a continuous flow of water, and a consequent increase in the quantity and variety of its natural food, its cubic dimensions 

 would probably have been twenty times greater ; yet it must have attained, prior to the lapse of a couple of years, to the usual period 

 of the adult state, (j. w.) 



