J 7 . l^ELE OS TOMES 



Similarity in eel-like form, e.g. as of Miirczna, is not in 

 itself indicative of direct kinship. {Apodes.) 



The Perch (Fig. i8i) has long been taken as a repre- 

 sentative Teleost. Perfect in its "lines," its compact, 

 wedge-like shape cleaves the water by vigorous thrusts of 

 a strong broad caudal ; its fins are stout, supported by 

 spinous rays ; its dermal armouring light, smooth, and flex- 

 ible ; its colour is brilliant under its transparent scales. 

 So adapted is it to its environment that its organ of static 

 equilibrium, the air-bladder, has lost its valvular connec- 

 tion with the gullet. Of existing fishes about one-half are 

 essentially percoid. {Acanthopterygii.) 



Fig. 182. — The codfi.sh, Gadus monhua, L. X -J. (After GOOUK in U. S. 

 F. C.) North Atlantic. 



The Cod (Fig. 182) is scarcely less important as a repre- 

 sentative Teleost. Its structural differences may perhaps 

 represent the result of a competition less active than that 

 of the perch in the struggle for survival. Heavy in body, 

 its sluggish form has become blunted and rounded ; its 

 fins are depressed, their rays soft and yielding; its scales 

 are reduced in size, colours less vivid ; its swim-bladder 

 loses its connection with the gullet. As many, perhaps, 

 as one quarter of the existing genera of fishes may be 

 assigned to this type. {Anacanthini.) 



The F/oti7ider (Fig. 183) should be mentioned as a singu- 



