OLD TYPES AND NEW 105 



d. Miss Durham s Intensified Mice 



Miss Durham, in her work with mice, has demon- 

 strated an intensifying factor, the absence of wliich 

 she calls a diluting factor. The action of the former 

 produces, as its name implies, intensity of color, 

 while that of the latter serves to lessen the degree of 

 intensity in which color appears. 



These factors of intensity and diluteness, it should 

 be observed, do not in any way correspond to the 

 duplex and simplex condition of a dominant color 

 character, either of which would straightway appear 

 if crossed with an albino. The factors of intensity 

 and dilution of color are of an entirely different 

 nature, as they have been proven to be indepen- 

 dently transmissible through albinos where a color 

 character could not appear because of the absence of 

 pigment. 



The following illustration of this kind of sup- 

 plementary factors taken from Miss Durham's 

 experiments will serve to make the case clear. The 

 symbols employed are : — 



B = black pigment which masks brown, or chocolate. 

 h = the absence of B, consequently chocolate. 

 I = intensity factor. 



i = dilution factor or absence of intensity. 

 C = a complementary color factor acting with P. 

 P = a complementary pigment factor acting with C. 

 BICP = black. 



BiCP = blue or maltese (dilute black). 

 hICP = chocolate. 

 hiCP = silver-fawn (dilute chocolate). 



