142 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



white mouse an albino of a yet different extraction. The following 

 scheme shows the ancestry of the pair so far as known : 



$ bl.-wh. l*2b. 9 wh. (? wh. 9 house mouse 



$ bl.-wh. 9 wh. 



I I 



$ bl. 92 9 gr. 91 



I I 



$ gr. 82 9 gr. 81 $ gr. 51 9 wh. 



i wh. 256 



9 wh. 192 



$ ch. 274 9 ch. 276 <? bl.-wh. 227 9 wh. 335 



$ ch.-wh. 392 9 wh. 447 



The single litter from this pair consisted of 5 young, of which 1 was 

 chocolate, 2 were gray, and 2 black. Assuming that the cliocolate 

 parent produced gametes having the chocolate character only, it is neces- 

 sary to suppose that the albino transmitted through some of its gametes 

 the black character only (producing the black offspring), and through 

 others the gray character (from the gray grandparents three generations 

 back). If some of the germ cells having the gray character should 

 produce by resolution gametes having the chocolate character only, the 

 chocolate class would be produced also. At all events, it seems clear 

 that the third or yellow element was contributed by the albino parent, 

 which in turn had inherited it from the gray mice on the maternal side. 



In order to test further the heredity of the chocolate character, the 

 writer mated together two of the gray heterozygotes coming from a cross 

 between chocolate mice and albinos, which in turn were the descendants 

 of a house mouse and the writer's original albino stock. The ancestry of 

 the albino parent of the two gray animals is as follows : 

 (J wh. 9 house mouse 



$ gr. 48 9 gr. 50 



$ wh. 152 9 wh. 132 



S wh. 254 



