Mother 



Father 



B 



D 



C white-yellow"^ X \ JP 



Figure 32. Diagram of results of breeding which show that the 

 X-chromosome consists of separable parts having different effects on 

 development. A female A, whose X-chromosomes j'ield red eyes and 

 gray body, is mated with a male B whose single X-chromosome yields 

 white eyes and yellow body. Their daughters C have together in the 

 same cell the two kinds of chromosomes, one yielding red and gray, 

 the other white and yellow. In some of the cells of such daughters 

 these chromosomes exchange parts, so that one now produces red 

 eyes and yellow body, the other white eyes and gray body. This is 

 demonstrated by the fact that such daughters produce a number of 

 sons (G and H) whose single X-chromosomes yield these new com- 

 binations together with many sons (E and F) in which the single 

 X-chromosome produces the original combination of characteristics. 



140 



