320 



HEREDITY 



all their offspring were pure white. But when blue fowls were 

 mated with others like themselves, some of their offspring were 



If a black Andalusian cock is mated with a white Andalusian hen, the offspring is a hybrid 

 showing a mottled blending of the black and white called blue. This is an example of incom- 

 plete dominance. If a blue cock is mated with a blue hen, 25 per cent of the offspring will 

 probably be black, 50 per cent may be blue, and 25 per cent may be white. Black pairs will breed 

 only black; the white pairs will breed only white ; but the offspring of a blue pair will segre- 

 gate, sort out, into black, blue, and white. 



black, some were white, and some blue. The blue chickens, then, 

 of the F2 generation were hybrids. 



The inheritance of color in the Andalusian fowl is : 



(1) Pure black mated with pure black will always produce pure 

 black. 



(2) Pure white mated with pure white will always produce pure 

 white. 



(3) Pure black mated with pure white will always produce 100 

 per cent blue hybrids. 



(4) Blue hybrids, when mated with blue hybrids, tend to pro- 

 duce 25 per cent black, 25 per cent white, and 50 per cent blue. 



The four-o'clock is another example of an organism in which a 

 hybrid, produced by two distinct species, is unlike either, but is a 

 blend of the two. The pure lines or types of four-o'clocks have 



