112 



THE AMERICAN NATURALIST [Vol. XLIX 



[ the Parents Were AI 



(Productivity 20 Per Day) X Zed <J (Productivity 6) 



6 Per Day) X PinJe 3 (Productivity 20) 



nber produced 



In most of these pairs the pink slightly exceeded the 

 3 : 1 expectation. In the few in which they fell behind, 

 the red (if we assume fertility to be the cause) might have 

 been of a higher fertility than the pink, as has been 

 explained. As a group, however, they give a proportion 

 somewhat below 3 : 1. 



In the next cross, the red fly was the more fertile. The 

 results are given in the following table: 



