No 

 50- 



40- 



30- 



20- 



10- 





 10- 



F,, DxW 



10 



I \ ^, I' , s l\ \ 



F2,DxW 



\\K\N 



20- 



10- 



xW 



. \\K\^k^-IV 



Grade, 



16 17 



Fig. 140. Graphic presentation of the variation in grade of two races of Dutch rabbits, "dark" (D) 

 and "white" (W), and results of intercrossing them. At the top is shown the grade distribution of 

 each uncrossed rac-e; below is shown the grade distribution of Fi animals, of Pz animals, and of animals 

 produced by back -crosses of Fi with each parent race. Note that the extracted D or W groups diverge 

 less from each other than the uncrossed D and W groups. 



