28 



INHERITANCE IN GUINEA-PIGS. 



red-eyed white male, 567, an F 3 descendant of the albino c? 54, race C, 

 was found to be homozygous for brown (table 17). What pigment his 

 eyes contained was undoubtedly brown, for when he was mated with 3 

 albino females descended from the albino cf 54, race C, he produced 1 

 silver cinnamon and 2 red-eyed chocolate young, besides 5 red-eyed 

 white and 8 albino young. The entire absence of black-colored young 

 indicates that this male, as well as his albino mates, transmitted the 

 capacity to form brown but not black pigmentation. When, however, 

 this same male (567) was mated with an albino derived from race B, 

 which never produces brown individuals, there were obtained 3 sepia- 

 colored young with red eyes, besides 7 albinos, showing that when the 

 mother transmitted black, this male produced black-pigmented young, 

 black being dominant over brown which he himself transmitted. 



TABLE 18. Results of mating a red-eyed white male ivith brown-eyed cream females. 



Both the males whose matings have just been described, viz, 567 and 

 576, were heterozygous in albinism, since when mated with albinos they 

 produced about 50 per cent of albino young. They were evidently of 

 the formula C r C a . If red-eyed white animals of this formula should 

 be mated with each other we should expect individuals to be produced 

 which are homozygous for red-eye, i. e., are of formula C r C r . Two 

 probably homozygous red-eyed females of this sort have been discov- 

 ered in mating red-eyed white animals inter se. One of them (9 726, 

 table 16) produced 10 young, all red-eyed white, in matings with c? 576, 

 known to be heterozygous for albinism. Had this female formed 

 albino gametes she should have produced 25 per cent of albino young 

 in the matings mentioned. It seems probable, therefore, that she did 

 not form such gametes. The F 3 9 775 (table 16) was probably like- 

 wise homozygous, since her mate is known to have been heterozygous 

 for albinism, but she produced no albinos in a total of 8 young. 



In the foregoing account nothing has been said concerning spotting 

 with white or with yellow ; nevertheless spotting of both sorts occurred 

 among certain of the F l and F 2 young obtained from the lea crosses. 

 Since the uncrossed lea race contained spotted animals of both sorts, it 

 is not surprising that the cross-bred descendants of this race should 



