FI 



the same arches of bone which support (he pectorals, 

 have the head large, and the whole of the anterior 

 part of the body thick and heavy, as compared with 

 the posterior. Some fishes are, no doubt, of such odd 

 shapes, and have so many extended filaments, and 

 other curious appendages, of which nobody knows the 

 use, attached to different, parts of their bodies, that we 

 are unable to apply any of the principles of our me- 

 chanics of simple forms to their singular structures ; 

 but still we find that, whenever the form of the rL-h i* 

 so simple that we can deal with it as we would do with 

 a common mathematical solid, we find that the above 

 stated principle applies ; and that, whenever the ven- 

 tral fins are brought forward near the throat, in aid of 

 the pectorals, the anterior end of the fish is always 

 the heaviest, and requires this additional apparatus for 

 the purpose of lilting it up. The plenyoptcrose fins 

 are at right angles to the axis of the body ; and thus, 

 while the posterior or progressively moving part im- 

 pels the fish forward, the accumulated fins under and 

 on the sides of the throat, strike downwards against 

 the water, and thus give an upward motion to the 

 anterior part of the body. Fishes which have this 

 enlargement of the head, and condensation of the 

 lateral or cross fins near it, are, generally speaking, 

 ground feeders ; and, when they are feeding, hang at 

 an angle with their heads lower than the hinder parts 

 of their bodies ; and, in this way, pick up mollus- 

 cous, and other small ground animals. Those fishes 

 which are altogether without ventral fins, and which 

 are sometimes styled apodul, or footless fishes, gene- 

 rally remain quietly at the bottom, and seldom ap- 

 proach the surface. They are all of the anguilliforme 

 or eel shape, with lengthened and slender bodies, and 

 the pectoral fins close to the head, and generally 

 lower down than in those fishes which have ventral 

 fins under the pectorals. The use of these pectoral 

 fins which are in general pretty much produced, is to 

 guide the head in any direction, upwards, downwards, 

 or laterally, and not chiefly for the purpose of raising 

 it, as in those which have the two sets of fins concen- 

 trated together near the same point. In most fishes 

 the motion in advance is not produced so much by the 

 stroke of the caudal fin as by the contrary throws of 

 the posterior part of the lengthened body ; and in 

 order that that may be a more effective swimming ap- 

 paratus throughout its whole length, the dorsal and 

 anal fins are, in general, continuous, and meet at the 

 extremity of the tail, where they in general form a 

 rounded or pointed terminal fin. 



Though ground fishes, those which have this struc- 

 ture are not exclusively, or even generally, ground 

 feeders. They range the waters near the bottom, but 

 they range them in line, and feed upon that which 

 moves in the water, rather than that which is quiescent 

 at the bottom. 



The principle now stated, and it is a very interest- 

 ing one, in what may be styled the mechanism of 

 - (one of the most interesting branches of natural 

 mechanics, because it presents us with motion directed 

 only against one resistance, that of the water), can- 

 not be better illustrated than bv a reference to Cuvier's 

 division of the Malacopterygii, or fishes with soft or 

 jointed rays to their fins ; and this allusion will at the 

 same time show the beauty of the systematic arrange- 

 ment, by that matchless adept in knowledge of the 

 structure and functions of animals. 



Cuvier divides this class into three families : 

 Abdominalcs, or those which have the abdominal or 



S H. 479 



posterior pair of fins placed backwards ; Subbrachia, 

 or those which have the second pair of fins placed 

 forwards, either immediately under the pectoral fins, 

 or sometimes in advance of them ; and Apoda, or 

 those in which the ventral fins are wanting. The 

 tribes of fishes which come under the first of these 

 families are the Cyprinidce or carp family, the Esocce 

 or pike family, the Silurules, the salmon tribe, and the 

 herrings and allied species. All of these are straight- 

 forward swimmers, and the greater number of them 

 are found near the surface of the water. They are, 

 generally speaking, what we are accustomed to call 

 handsomely proportioned fishes, rather long than 

 otherwise, and, generally speaking, they are rapid in 

 their progressive motions, and not remarkable for the 

 facility with which they can plunge to great depths, 

 or rise from them. 



The second family, or those which have the ven- 

 tral fins concentrated near the pectorals, and, generally 

 peaking, articulated to or connected with the bones 

 of the shoulder, comprehend the cod family in all its 

 genera ; the flat fishes, or different species of floun- 

 ders, soles, turbots, and other genera and species of 

 that type ; and the discoboli, or those fishes which 

 have the vential fins formed into a sort of round disc 

 on the under part of the body. All these are bank 

 fishes to some extent or other, or if they are not found 

 on banks of sand or mud, they frequent rocky places ; 

 and, generally speaking, feed near the bottom. la 

 most of the species they are not very discursive, but 

 remain on the same grounds, often accumulating in 

 vast numbers ; and one of the chief uses of the con- 

 centration of the four lateral fins at the anterior part 

 of the body appears to be, to enable them to get over 

 the inequalities of that bottom over which they find 

 their food. The flat fishes deserve perhaps a parti- 

 cular notice on account of the particular position of 

 their bodies when swimming, which is really with the 

 side uppermost, and not the back, though the upper 

 surface is coloured like the backs of ordinary fishes, 

 and the under surface like the belly. There, is how- 

 ever, a twist, at the insertion of the head, which gives 

 a very peculiar appearance to that part of this tribe 

 of fishes ; but it will be better to notice their general 

 characters in a separate article FLAT-FISH, than to 

 break the chain of illustration in the present one, or 

 extend it to greater length. 



The third, or apodal family of this order, consists 

 entirely of elongated or eel-shaped fishes, which, like 

 the former are ground-fishes, and perhaps upon the 

 whole remain constantly nearer the ground than 

 they ; but they swim by contrary flexures of the 

 body, and not by the stroke of the tail, as an oar. 

 There is sometimes a vulgar prejudice against this 

 class of fishes, in consequence of their snake-like 

 form, and snake-like movements. The slightest at- 

 tention will, however, suffice to convince any one that 

 their motions are those of true fishes, and not of 

 ophidian reptiles, even aquatic ones. The motion 

 of these reptiles is always in the vertical plane, so 

 that, even when they swim, the flexures or bendings 

 of the body are upwards and downwards. Those of 

 the apoda'l fishes, even of the most snake-like of 

 them, are, on the other hand, always lateral, and 

 they have little or no power ef bending the body in 

 the'direction of the mesial plane, that is, in the direc- 

 tion of the edge of this plane. In passing we may 

 here remark, that the curved form given by painters 

 to their imaginary dolphin is perfectly inconsistent 



