COLOR 



63 



The 4 remaining varieties would be identical with these 4 except as 

 regards the factor U, in which they would be heterozygous, U(S), instead 

 of homozygous, U 2 . 



We have determined the zygotic formulae of 2 blue rabbits only, both 

 of which were produced in the course of our experiments. One (c? 1434, 

 table 42) was of variety 3, the other (<? 1228, table 43) was of variety 4. 



We shall pass by the spotted black and spotted blue varieties of rabbit, 

 of both which sorts a certain number of individuals have been produced 

 in our experiments, but which have not been thoroughly tested. 



TABLE 43. Matings and young of 3 1228, blue. 



YELLOW. 



Yellow rabbits differ from gray ones only in the factor E (extended 

 black or brown pigmentation), in place of which they bear the alternative 

 condition R (restricted black or brown pigmentation). Since R is reces- 

 sive in relation to E, yellow rabbits are invariably homozygous, R 2 , as 

 regards this factor. Theoretically sixteen different varieties are possible, 

 as follows: 



(1) Yellow producing yellow only; formula, 



(2) Yellow producing yellow, and white; formula, 



(3) Yellow producing yellow, and sooty; formula, B 2 Br 2 R 2 AC 2 I 2 U 2 Y 2 . 



(4) Yellow producing yellow, sooty, and white; formula, B 2 Br 2 R2ACI 2 U 2 Y 2 . 



Four other varieties should differ from these 4 in factor I only, being 

 I(D) instead of I 2 , and producing dilute as well as intensely pigmented 

 individuals. Eight others should differ from these eight in producing 

 spotted as well as uniformly pigmented individuals. We shall content 

 ourselves with giving examples of the first four varieties enumerated. 



Variety i produces only yellows when mated with other yellows or 

 with sooties, and only yellows and grays when mated with blacks or blues 

 of any sort whatever. It is represented in our yellow c?38i, a son of 2 

 gray rabbits of variety 5, viz, 9 175, and c? 176. He was mated with 6 

 different yellow females, 3 of which had produced sooty offspring by other 

 mates, and there resulted 61 young, all yellow. In matings with 2 differ- 

 ent sooty females he produced 12 young, all yellow; and in a mating 

 with a gray female of variety 6 ( 9 178) he produced 3 yellow and 6 gray 



