184 



FISHES. 



It will be evident, from the foregoing remarks, that the 

 amount of variation within the limits of the same species — 

 either due to the natural growth and development, or to 

 external physical conditions, or to abnormal accidental cir- 

 cumstances — is greater in fishes than in any of the higher 

 classes of Vertebrates. The amount of variation is greater 

 in certain genera or families than in others, and it is much 

 greater in Teleosteans and Ganoids than in Chondroptery- 

 gians. Naturally, it is greatest in the few species which 

 have been domesticated, and which we shall mention in the 

 succeeding chapter. 



rig. 96. — Chimsera colliei <?, -west coast of North America. A. Front view of 

 head. B. Palate, a, Peritoneal aperture ; b, Nostrils ; c, Vomerine teeth ; 

 d, Mandibular teeth ; e, Palatine teeth ; /, Claspers. 



