passes over the egg, difTusiug the secretion from the niilts, and fecun- 

 dating the eggs (a). 



Of all the classes of animals, that of fishes is the most difficult to sub- 

 divide into orders from fixed and sensible characters. After many at- 

 tempts I have decided upon adopting the following arrangement, which, 

 though it militates in some instances against precision, does not separate 

 natural families. 



Fishes form two distinct series, that of Fishes, properly so called, and 

 that of the Chondropterygii, otherwise called Cartilaginous Fishes. 



The general character of the latter consists in the absence of the bones 



fS^° (a) In the great work on Icthyology, by Cuvier, now in the course of publi- 

 cation, he dwells at much greater length on the general characters of the Fishes. 

 The following passage, which we translate from that work, will be read with much 

 interest: — 



" Being aquatic, that is to say, living in a liquid which is heavier, and offers 

 greater resistance than air, their power of motion has been necessarily disposed and 

 calculated for progression as well as for elevation, which is also accomplished by them 

 with ease. Hence arisi;s that form of body which offers least resistance, the chief 

 seat of muscular force residing in the tail, the shortness and expansibility of their 

 limbs, the membranes which support them, the smooth or scaly teguments, and the 

 total absence of hairs or feathers. Breathing only through the medium of water, that 

 is, for the purpose of giving an arterial nature to their blood, profiting by the small 

 quantity of oxygen contained in the air, which is mingled with the water, their blood 

 is necessarily cold, and their vitality, the energy of their senses and movements, are 

 consequently less than in Mammalia and Birds. Their brain, therefore, or rather a 

 composition similar to it, is proportionably much smaller, and the external organs of 

 their senses are not of a nature to admit of powerful impi-essions. Fishes, in fact, 

 are, of all vertebrated animals, those which have the least apparent signs of sensibi • 

 lity. Having no elastic air at their disposal, they remain mute, or nearly so, and all 

 those sensations awakened or sustained by the voice remain unknown to them. 

 Their eyes almost immoveable, their bony and rigid countenance, their limbs de- 

 prived of the power of inflexion, and every part moving at the same time, deprive 

 them of the faculty of varying their physiognomy, or expressing their emotions. 

 Their ear, inclosed on every side by the bones of the skull, without external conch 

 or internal labyrynth, and composed only of a sac and membranous canals, scarcely 

 allows them to distinguish the most striking sounds; and, in fact, an exquisite sense 

 of hearing would be of very little use to those destined to live in the empire of silence, 

 and around whom all are mute. Their sight, in the depths of their abode, would be 

 little exercised, if the greater number of the species had not, by the size of their 

 eyes, been enabled to supply the deficiency of light; but, even in these species, the 

 eye scarcely changes its direction; still less can it change its dimensions, and accom- 

 modate itself to the distance of objects; its iris neither dilates nor contracts, and its 

 pupil remains the same in every degree of light. No tear bathes this eye, no eyelid 

 soothes or protects it; and, in this class, it nuist be regarded as only a feeble rej^re- 

 sentation of that beautiful, brilliant, and animated organ of the higher classes of 

 animals. Procuring food by swimming after a prey which itself swims with greater 

 or less rapidity, having no means of seizing this prey but by swallowing it, a delicate 

 sense of taste would have been useless to fishes had nature bestowed it on them. But 

 their tongue, almost imaioveable, often bonj', or amied mth dentated plates, and 

 only receiving a few slender nerves, demonstrates that this organ is as little sensible 

 as it is little necessary. Smell even cannot be as continually exercised by fishes as 

 by animals which breathe air in a direct manner, and whose nostiils are unceasingly 

 traversed by odoriferous vapours. Lastly, we come to the touch, which, on account 

 of the surface of their bodies being encircled by scales, by the inflexibihty of therays 

 of their limbs, and by the dryness of the membranes enveloping them, has bee n 

 obliged as it were to seek refuge at the end of their lips; and even these, in some 

 sjiecies, are reduced to a dry and insensible hardness." — Eng. Ed. 



