HEREDITY 



plainly visible. A cross with a black race 

 makes it visible. No one, however, has suc- 

 ceeded in " fixing '' a blue race, that is, 

 in obtaining a strain which would breed 

 true. 



When two blue individuals are bred together 

 they produce black, blue, and white offspring 

 in the ratio 1:2:1. The blacks are homo- 

 zygous, B B ; the whites also are homozygous, 

 WW, but the blues are invariably heterozy- 

 gous, B W. Blue accordingly in this case is 

 called a heterozygous character, one which is 

 due to the presence in one zygote of two unlike 

 unit-characters, which invariably segregate from 

 each other at the genesis of gametes, but which 

 jointly produce a different appearance from 

 what either produces by itself. If a strain of 

 Andalusian fowls should ever be secured which 

 would breed true, it would have to come about 

 by the association of black with white in a 

 non-segregating relationship, so that both 

 would be transmitted in the same gamete. 

 That is, one would have to secure in the same 

 gamete with white enough black pigment to 

 bring out the latent mosaic pattern, and fur- 



56 



