THE NATURALIST. 



YCHTHYOLOGY. 



THE NATURAL HISTORY OF FISHES. 



THE study of fishes, technically termed Ychthyology, was, perhaps, longer in being 

 brought to what might be called a science, than the histories and descriptions of animals 

 and birds. The difficulty of procuring a numerous series of individuals, and the impos- 

 sibility of penetrating and pursuing them in the deep recesses of the ocean, withdrew 

 the constant charm which novelty of form threw over the branches constituted by those 

 animals which inhabited the same element with ourselves. 



Living in a different element from that which maintains most of the mammalia and 

 birds, we find the external covering of fishes to consist of plates, or scales, supplying 

 the place of hair or feathers. The skin of fishes completely surrounds the body, clasp- 

 ing close to the muscles, and serving as an outward skeleton, as the bones do for a pro- 

 tection to the inward parts. The scales are composed of two substances, the one allied 

 to that of horn, the other to that which forms the enamel of teeth. 



The scales are held in position by a fold of the epidermis, often so delicate as scarcely 

 to be visible, but which covers almost the whole part of the fish exposed to our view. 

 They fold over each other in different modes of imbrication ; sometimes regularly, like 

 the tiling of a house ; sometimes in a lateral form, or with the lower longitudinal edge 

 folding over the upper edge of the scale below; sometimes alternately, so that the join- 

 ing of the preceding scale is opposite the centre of that which follows, while in others 

 there is no imbrication at all, and the edges meet like plates, or the flags of a pavement. 



The Baron Cuvier assumes the common perch among fishes as the form in which the 

 greatest general perfection is exhibited, (see plate No. 1,) and being a species familiarly 

 known to every one, will serve to convey an idea of this class of beings. 



In the perch, and indeed in all those fishes which are endowed with extensive loco- 

 motive powers, or require swiftness to seize their prey, the tail is the great organ of 

 motion, while the fins are the balancers or directors, a contrary arrangement to that 

 shown in the members of those creatures of the land and air, where the tail is the 

 director or helm, the feet and wings the movers. The fins on the upper surface serve 

 to balance the body, those of the lower surface to turn it, to move it slowly, and to 

 keep it suspended in strong currents ; but in all these, the motion or assistance of the 

 tail is ,observable. In very swift motion the fins are quiet ; the creature could not keep 

 them extended, far less use them, and they fold closely to the body, and offer no re- 

 sistance to its rapid passage through the water. 



The senses among fishes may almost be said to be confined to three those of seeing, 



