COLOR 



55 



rabbits of this sort are readily produced by mating a gray rabbit with a black 

 one. A rabbit of this sort produced in a slightly different way was our gray 

 o" 2005, which, when mated with a sooty yellow (9 1471), produced a litter of 

 3 black and 2 gray young; likewise our gray rf 2004, which, when mated with 

 sooty yellow 9 1491, produced 5 black and 5 gray offspring (exactly the expected 

 equality of blacks and grays). Many Belgian hares are of this second variety 

 ("throwing blacks," as well as grays, but not other colors). 



(3) A third sort of gray rabbit produces (when mated with animals like itself) 

 albino offspring as well as gray ones, but none of other colors. It is heterozygous 

 (single) in C, but otherwise homozygous. Its formula is B 2 Br 2 E 2 A 2 CI 2 U 2 Y 2 . 

 We have at the present time some rabbits believed to be of this kind, but they 

 are as yet not fully tested. Hurst (105) also describes rabbits of this variety. 



(4) A fourth sort of gray rabbit produces * young of the varieties gray, black, 

 and white only. It is heterozygous (single) in A and C, but not in other factors. 

 Its formula is B,Br 2 E 2 ACI 2 U 2 Y 2 . It is represented in our rabbits (9 1161 and 

 c? 1172) produced by a cross between a white rabbit (of gray ancestry) and a 

 heterozygous gray one. Mated with each other these two produced 17 young, 

 distributed as follows: 10 gray, 3 black, and 4 white (expected 9:3:4). Male 

 1172 was mated also with a white female of black parentage (9 789), and pro- 

 duced 3 gray, 5 black, and 2 white offspring (expected 1:1:2). 



Rabbits differing from variety 4 only in the respect that the albinos which 

 they produce are of the Himalayan type are represented in our gray 6" 48, and 

 9 49 and 9 50. They were produced by the mating of the Belgian hare 9 431 

 with a Himalayan (<? 8). The result of their matings inter se is given in table 32. 



TABLE 32. Matings and young of c? 48, gray. 



1 Expected ratio of 9: 3 : 4, giving in this case 27: 9: 12. 



The formula of such rabbits may be expressed by adding the symbol C' to 

 the formula as given for variety 4, viz, B 2 Br 2 E 2 AC(C / ) I 2 U 2 Y 2 . 



TABLE 33. Matings and young of gray 9 175. 



(5) A fifth sort of gray rabbit produces young of the varieties gray and yel- 

 low, but none of other colors. It is heterozygous (single) in the extension factor 

 E, carrying as an alternative (recessive) character R (restricted distribution of 

 black and brown pigments). Its formula accordingly is B 2 Br 2 E(R)A2C 2 I 2 U 2 Y 2 . 



1 When on this and subsequent pages the nature of the mating is not specified it will be under- 

 stood that the mating is with animals of its own variety or of varieties recessive to its own. 



