THE CELL-DOCTRINE 



135 



Black 

 100 % 



25 % Black 50 <f> Blue 25 f> White 



Black 100 



as above 



100 % White 



The same in subsequent generations 



FIG. 17. Mendelian Heredity in Coloration of Blue Andalusian Fowl. As 

 shown by the figure the blue andalusian cannot be established as a breed, 

 because it is the hybrid produced by crossing a black and a white breed 

 together and because Mendelian segregation is continually separating 

 out pure whites and blacks in subsequent generations. The breeder 

 can, however, secure 100 per cent of blue andalusians by crossing the 

 white and black. P', first parental generation; F', etc., first filial and 

 subsequent filial generations. 



