50 HIGH SCHOOL ZOOLOGY. 



pels it by way of the gills throughout the entire system. The sense- 

 organs, lins, myotomes, and heterocercal tail are all evident, and event- 

 ually the yolk is all absorbed and the young fish begins to feed for itself. 

 At the end of three months the form of the adult is attained, although 

 the fish is hardly an inch in length. Teleosts differ very materially as 

 to the length of time of hatching of the egg, and the rapidity with 

 which the developmental processes run, but there is always less food- 

 yolk than in certain other groups of fishes to be afterward referred to, 

 where the development is much slower. 



