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THE AMERICAN NATURALIST [Vol. XL VII 



color reds 9 (mainly red), 482, 496, 497, 527, 596, and one 

 individual, 526, much like the bicolor reds, but with a 

 minute spot of black. It is noteworthy that although 



black entered into the original cross from one side it was 

 not recovered except for the small spot of black on 526. 

 Yet uniform black is described as dominant to red. If 

 401 was heterozygous for the black factor (as a single 

 factor) black would not necessarily be expected. Only 

 against this view is the fact that her matings with tri- 

 color did not indicate this, and the small black spot on 

 526 could not be explained if this assumption were true. 



One back-cross between 526$ with her father, 427 c?, 

 gave one bicolor red, 576; and 577 (red, partially de- 

 stroyed when found) and 578, classified as red. 



On the other hand, when tricolor black 401 ? was mated 

 to self black, 309 (Horton's stock), one young was pro- 

 duced, a self-colored black. In this case also uniform 

 dominates, but the color is black. 



No. 401 $ was also bred to another black male, and pro- 

 duced one black, 544, one red, 545, and one tortoise, 546. 

 This male appears to have been homozygous as regards 

 lack of spotted white, heterozygous for black (B b), and 

 also heterozygous for some factor that causes black to 



• On the whole the bicolor reds produced in F, when uniform was crossed 

 and the white tends to occur on the anterior portion of the body. 



