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, 6, swift movin^com- 

 pressed, fusiform; c, d, e, elongated, swift, fusiform types, grading into/, 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- 



