No. 5S4] HEREDITY AND ITS MEANING 



471 



Suppose, however, that a change in the germ plasm has 

 occurred (Fig. 2) at some time or other. In one member 

 of the first pair of chromosomes, determinant "A" has 

 become "a." The mature germ cells differ from each 

 other by one factor. For this reason the plant does not 

 breed true, but gives a mono-hybrid Mendelian result. 



