300 LUTHER BURBANK 



Thus it is found that in the case of mice, for 

 example, whereas blackness of coat is dominant 

 over whiteness, just as in the case of the guinea 

 pigs, blackness itself may be overlaid, as it were, 

 and entirely obscured by the presence of factors 

 for gray coating, and it further appears that 

 yellow pigment may dominate the gray coat as 

 well as the black. 



A further complication occurs in that an ani- 

 mal that is neither yellow nor gray nor black may 

 be chocolate in color. And it is only in case this 

 color also is absent that the mouse will be white. 



Moreover, if the factors for chocolate are ab- 

 sent, the factors for grayness and blackness may 

 neutralize each other, and exist in what is called 

 a masked condition, neither one being able to 

 make itself manifest on account of the presence 

 of the other, because both are dominant factors; 

 so that the mouse will be white, yet will carry the 

 factors for grayness and for blackness masked in 

 its germ plasm. 



When the chocolate factors are present, how- 

 ever, in addition to the factors for blackness and 

 grayness, the presence of three dominant color 

 factors has the curious effect of enabling one of 

 them, in this case gray, to make itself manifest. 



So the chocolate factor is necessary to produce 

 a gray mouse; and the chocolate-colored mouse 



