128 PROCEEDINGS OF THE AMERICAN ACADEMY. 



('95) for the black-white Japanese waltzing mice which he bred. In 

 general, therefore, the black type seems to be a definite one which breeds 

 trne to tliat pigment character, and does not show the presence of the 

 yellow pigment. 



The cross of the black with the albino type is one of considerable in- 

 terest. Haacke ('95) bred black-white mice of a stock imported from 

 Japan to some albinos whose ancestry is unrecorded, and obtained usually 

 gray mice indistinguishable from the wild gray ones. More rarely, a 

 wholly black mouse came of this same union. Von Guaita ('98, : GO) 

 repeated the experiment, crossing black-white Japanese dancing mice with 

 an inbred stock of albinos. He obtained twenty-eight young, all uni- 

 formly gray like the house mouse. A like result is recorded by Dav- 

 enport (; 04), only gray young having resulted in two litters from 

 black mice bred to albinos. 



In the writer's experiments, as previously recorded (Castle and Allen, 

 : 03), two black-white mice were crossed with albinos, the result being 

 that some of the offspring were gray, others black. The spotted 

 animals were both males and were known to give only black-white 

 young when bred to mice of that color character. Their gametes, 

 then, did not transmit the yellow pigment character, and the above 

 result shows the same to have been true also of some at least of 

 the gametes of the albinos, for there were in all 15 black young in addi- 

 tion to 28 gray ones. An explanation of this result is suggested as 

 follows : Since the black mice produced gametes having only the black 

 character (or rather, black-chocolate), it is clear, on the present hypothe- 

 sis, that some of the albinos were producing gametes with only the black 

 character, while a large number were producing gametes whose union 

 with those of the black mice brought together all three pigment char- 

 acters, resulting in the production of gray young. If we suppose that 

 the albinos used came of a mixed ancestry, as seems probable, and that 

 one-half the gametes formed by them contained latent the complex gray 

 character, while in the other half the latent gray element underwent 

 resolution, the following combinations of pigment characters would result 

 from the mating described : 



a. 



bl.-ch. -f- bl.-ch. = gametes of $ , 



wh. (gr. latent) -f wh. (gr. latent) =^ gametes of 9 ■> 



4gr. = Fi. 



