21 A Adaptations of Fishes 



form. Water life is less exacting than land life, having less vari- 

 ation of conditions. It is, therefore, less effective in pushing 



Fig. 1.5.5. — Skeleton of Red Rockfish, Sehastodcs miniatus Jordan and Gilbert. 



California. 



forward the differentiation of parts. AVhen vertebrse are few 

 in number each one is relatively larger, its structure is more 

 complicated, its appendages larger and more useful, and the fins 

 with which it is connected are better developed. In other words, 

 the tropical fish is more intensely and compactly a fish, with a 

 better fish equipment, and in all ways better fitted for the busi- 

 ness of a fish, especially for that of a fish that stays at home. 

 In the center of competition no species can aff'ord to be 

 handicapped by a weak back-bone and redundant vertebrse. 



Fig. 156.— Skeleton of a spiny-rayed fish of the tropics, Holacanthus ciliaris 



(Linna-us) . 



Those who are thus weighted cannot hold their own. They 

 must change or perish. 



The conditions most favorable to fish life are among the rocks 



