152 



FISHES 



In Fishes the characteristic shape of the body is more or less 

 that of a spindle, tapering at each end and somewhat flattened 

 from side to side ; and, as a rule, the three regions of the body- 

 head, trunk, and tail pass almost imperceptibly into one another 

 (Fig. 93, A). Nevertheless, there is great diversity of form in 

 different Fishes. Compare, for example, the elongated, cylindrical 

 shape of the Eels (which is perhaps associated with their habit of 



n. 



a.J 



FIG. 93. Tilapia dolloi. To show the external characters of an Acanthopterygian 

 Teleost. A, side view ; B, the first branchial arch. aj~, Spinose part of the anal 

 fin ; a./ 1 , soft rays ; c.f, caudal tin ; d.f, spinose portion of the dorsal fin ; d.f 1 , 

 soft rays ; g.f, gill filaments ; g.r, gill rakers ; i.l.l, inferior lateral line ; n, nostril ; 

 p.f, pelvic fin ; p.op, preoperculum ; pt.f, pectoral fin ; s.l.l, superior lateral line ; 

 t.s, transverse row of scales. (From Boulenger.) 



insinuating themselves into holes and crevices, and their undula- 

 tory, snake-like movements when swimming); the compressed, band- 

 like shape of the Eibbon-Fishes (Trachypteridae) ; the flattened 

 bodies of those Fishes which habitually live and move on the 

 bottom, like the Skates and Eays ; the thin, laterally-compressed 

 bodies, often nearly as high as long, of the Fiat-Fishes (Pleuro- 

 nectidae), which always swim and rest on either the right or left 

 side ; the almost spherical Globe-Fishes (Tetrodon) which often 

 float passively in the water ; and the singular rectangular, 

 coffin-like Coffer-Fishes (Ostracion). There is also much differ- 

 ence in the relative proportions of the three regions of the 

 body in different Fishes, as witness the enormous size and 



