PISCES 



99 



than that of terrestrial animals, tend to radiate adaptively in several 

 main and many minor directions. This has occurred not once in the 



Fig. 53. — The principal types of body form in fishes, a, b, swift moving com- 

 pressed, fusiform; c, d, e, elongated, swift, fusiform types, grading into — f, g, elong- 

 ated eel-like forms; h, i, laterally compressed, slow moving, deep-bodied; j, k, I, lat- 

 erally depressed, flat, bottom-feeding. (After Osborn's " Origin and Evolution of 

 Life." [Charles Scribner's Sons].) 



evolution of fishes, but many times. Every large group of fishes ex- 

 hibits "adaptive radiation" in Osborn's sense; for we find in nearly 

 every order of fishes the swift fusiform types, the short laterally com- 



