124 EVOLUTION AND GENETICS 



the two races of corn are known to belong to a tall 

 and a short race respectively. Here, then, the chief 

 effect or difference is due to heredity. On the other 

 hand, if individuals of the same race develop in a 



Fig. 57, — A short and a tall boy, each holding a stalk 

 of corn. The short boy holds a stalk of a race of short corn, 

 and the tall boy one of tall corn. (After Blakeslee.) 



