ALLEN. — THE HEREDITY OF COAT COLOR IN MICE. 133 



heterozygotes of house-mouse and albino parentage. Two of the black 

 mice had albiaism recessive, the third, though born in the same litter, 

 produced no albinos. The ancestry of the albinos used iu this cross is 

 shown in the following diagram : 



c? wh. ^ ^>«"^^ <? wh. ^ ^""^^ S wh. ^ ^°"^^ 



mouse mouse mouse 



I I 1 I I 1 



<? gr. 48 9 gr. 50, 52 ^ gr. 48 9 gr. 50, 52 



^ gr. 51 9 wh. 



9 wh. 234 I I Jwh. 142 9 wh, 141 



c? wh. 152 9 wh. 132 I I 



9 wh. 255 i wh. 202 9 wh. 204 



(? wh. 246 



From each of these three pairs of black and albino mice, both gray 

 and black young were obtained, the total being 10 gray, 4 black. There 

 were also 16 albinos, as well as two which were dark-eyed but died 

 before attaining the coat pigments. Here, again, if it be assumed that 

 one-half the gametes of the albino contain the gray character and that in 

 the other half segregation of this character takes place, so that at least 

 one-quarter of all the gametes produced have the black character, then 

 one in four of the pigmented offspring should be black, the others gray. 

 In the experiment, 4 out of 14 mice were black, the number demanded 

 by the hypothesis being 3.5. 



In a similar case, where black animals from spotted stock were bred 

 to the writer's original lot of albinos, there were produced 4 gray mice 

 and 1 black one in addition to 3 albinos. The evidence therefore favors 

 the idea that the albino may transmit the gray character entire in a 

 certain proportion of its gametes, while the rest transmit regularly only 

 certain components of that character. 



In the course of these experiments, it was found that two black mice, 

 if paired, produced only black young, even though one parent had the 

 character albinism recessive. Since one-half the unions in this case take 

 place between gametes containing respectively the albino and the black- 



