CHARACTERS IN HEREDITY 151 



ingly numerous, but for our purpose may be 

 reduced to four fundamental color types in addi- 

 tion to the albino or uncolored type. These four 

 are gray, black, yellow, and sooty yellow. The 

 last I shall for simplicity call sooty. Gray is the 

 original or wild type from which the others have 

 been derived. The gray fur contains both black 

 and yellow pigments, but so disposed as to pro- 

 duce a pattern on the individual hair, viz., a dark 

 base and tip and in between them a band of yel- 

 low. The lower surfaces of the body also are 

 whitish. In the black variety the hair pattern is 

 wanting, and the black pigment occurs through- 

 out the length of each hair and all over the body. 

 In the yellow variety black pigment is largely 

 wanting throughout the coat, though present in 

 the eye and, in very small quantities, in the hair. 

 The presence of the hair-pattern is nevertheless 

 suggested by whitish under surfaces, as in the 

 gray type. The sooty type closely resembles the 

 yellow, but has colored under surfaces, instead of 

 white ones. Yellow and sooty correspond with 

 gray and black respectively, but with a greatly 

 reduced amount of black pigment in the fur, so 

 that yellow predominates there. 



Let us now consider the relation of these four 

 types one to the other. Gray crossed with any 

 other type produces only gray offspring. Black 

 crossed with yellow produces gray, but crossed 

 with sooty produces black. Yellow crossed with 

 sooty produces only yellow. Sooty disappears 



