HEREDITY 



poultry. The various combinations are of 

 course brought about by crossing, and two gen- 

 erations suffice theoretically for securing them. 



In mice, if one possessed only the albino 

 variety last described, — the one which corre- 

 sponds with the brown-eyed yellow variety, — 

 he could easily produce within six months every 

 one of the various color varieties which have 

 been mentioned. All he would have to do 

 would be to catch some wild mice and cross 

 these with his albinos. The immediate off- 

 spring produced by the cross might seem un- 

 promising; they would either be gray, exactly 

 like wild mice, or else yellow. But if our 

 breeder possessed the faith to breed a second 

 generation from these animals, he would be 

 rewarded by seeing all the color varieties which 

 I have described put in an appearance, viz. 

 yellows with black eyes, and yellows with 

 brown eyes, blacks, browns, cinnamons, and 

 grays, and albinos corresponding in character 

 with each colored variety except for the lack 

 of the color-factor C. 



It may be of interest to consider how some 

 additional color varieties of mice have arisen, 



78 



