28 COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



centripetal pigmentation associated either with agouti or with black 

 pigmentation (for the latter combination 9 1035 is specific evidence) , 

 and albinism associated probably either with agouti or with black pig- 

 mentation (these of course being in a latent condition). It seems from 

 this and other similar cases that the regional distribution of pigments 

 on the body (centripetal vs. albino) is something inherited independ- 

 ently of the specific character of the pigments formed. Albinism 

 vs. centripetal pigmentation forms one pair of alternative (Mendelian) 

 characters ; agouti vs. black pigmentation forms another pair. An 

 animal like 2020, then, is a dihybrid as regards pigment characters, 

 and should form in equal number gametes of four different sorts, viz, 

 albino [black latent],* albino [agouti latent], centripetal agouti, and 

 centripetal black. This idea is supported by Allen's ( : 04) observations 

 on mice, and finds frequent illustrations in these experiments. 



Agouti x red. I have made this mating between pure parents only 

 once. Agouti ? 2019, mated with red cf 2054, produced 4 young, 3 of 

 them agouti > red, i red > agouti > white. This result indicates a 

 tendency of agouti to dominate over red, or at least to mask the presence 

 of red. In this experiment, the mother, 9 2019, had a red hip patch. 

 The occurrence of red and of white spots on the young was probably 

 due to a mosaic character of certain of her gametes rather than to 

 some peculiarity of the father, a self red. 



One of the young produced by this cross, viz, agouti > red 9 1294, 

 when mated with her red father, c? 2054, produced 6 young, 2 agouti 

 > red, i red > agouti, 2 red-black, and i red, indicating segregation of 

 the respective agouti > red, and red characters brought together in the 

 previous generation, so as to allow of the formation of pure red gametes. 

 The occurrence of two red-black young indicates that in some cases 

 the agouti character may break up into isolated black and red under 

 the influence of the cross. 



Agouti x albino. Pure agoutis mated with albinos of spotted or of 

 unknown ancestry have produced only animals predominantly agouti- 

 colored, though the offspring have in some cases had one or more of 

 the typical color patches red or white, but never black or chocolate. 

 The spotting with red or white was inherent in the agouti stock used. 



It is probable that in no case did the albino parent in these crosses 

 transmit latent agouti. This statement is based on the results of 

 other crosses made with these same albino animals, as well as on an 

 examination of their pedigrees. If this assumption is correct, there is 

 seen in this experiment a strong tendency for the agouti character to 

 dominate over other pigment characters contained latent in albino gam- 

 etes ; for every one of the 17 young was agouti-pigmented. 



* Brackets will be used to indicate latent characters, just as parentheses to 

 indicate recessive ones. 



