4 THE THEORY OF THE GENE 



be two kinds of offspring, tall and short in equal numbers 

 (Fig. 2). The results confirm the expectation. 



The same relation shown by the tall and the short peas 

 can be illustrated by the inheritance of eye color in man. 

 Blue eyes mated to blue, give only blues; brown eyes 



F 



brbl 



_yv_ 



Germ cells of Y 



Fi£ and 6 bf> bl 



d 



Fig. 3. 

 Inheritance of brown eyes (brbr) versus blue (blbl) eyes in man. 



bred to brown give only brown, provided the browns 

 have had only a brown ancestry. If a blue mates with a 

 pure brown, the children are brown (Fig. 3). If two indi- 

 viduals that have arisen from such parentage marry, 

 their children will be brown- and blue-eyed in the ratio 

 of 3 to 1. 



