80 BIOLOGY AND SOCIAL PROBLEMS 



appear in the offspring unmixed and in highly 

 significant proportions. Thus in guinea-pigs 

 the white coat-color of a pure albino stock 

 and the black coat-color of a pure melanic 

 stock can be made to associate by crossing 

 these two stocks. The animals that result 

 from this cross are not, as you well know, gray 

 individuals midway between the white and 

 black parents, but all strictly black individ- 

 uals to all appearances like their black an- 

 cestor. That they are not, however, exactly 

 like this ancestor is seen from the fact that 

 when they are bred among themselves, in- 

 stead of producing nothing but black indi- 

 viduals as their black parent would have done 

 if mated with his kind, they bring forth pure 

 white stock as well as black stock and in the 

 proportion of one of the former to three of 

 the latter. Thus these black individuals can 

 be shown to carry hidden in their bodies the 

 white characteristic, though they show noth- 

 ing of this on their exteriors. Of such pairs 

 of characteristics, the one which may thus be 

 hidden is spoken of as recessive, the other 

 dominant. (Plate II.) 



The black and the white descendants of 

 such individuals occur in the very remarkable 



