54 



INHERITANCE IN RABBITS 



F,, and in F 2 gray, black, and Himalayan, but no other varieties. Whether it 

 is possible to associate A with the other factors found in a Himalayan rabbit 

 remains to be demonstrated. 



The reader will naturally expect some concrete evidence in support of 

 the gametic composition ascribed to the various color varieties in the fore- 

 going enumeration. To a consideration of this we may proceed immedi- 

 ately. It would be wearisome to describe in detail all the experiments 

 which have been made in the investigation of this matter. They have 

 involved the production in various sorts of matings of some thousands of 

 rabbits. It will suffice, we think, to cite from our experiments certain 

 matings which were of such a nature as to test the validity of our hypotheti- 

 cal formulae. 



ZYGOTIC VARIATION WITHIN EACH COLOR VARIETY. 



GRAY. 



The formula has already been given of a gamete which transmits the 

 coat characters of a wild gray rabbit. It contains, as we have seen, 8 

 distinct factors. Such a gamete might be produced by gray rabbits of 

 many different sorts, all of which look alike but breed differently, i. e., 

 which have a different zygotic composition. 



(i) The first sort which we will consider is homozygous (double) as regards 

 each factor which enters into the composition of the gamete transmitting gray. 

 Its zygotic formula is B 2 Br 2 E 2 A 2 C 2 I 2 U 2 Y 2 (compare diagram, p. 51). Every 

 gamete which it forms transmits, therefore, all the components of a gray coat. 

 This is the condition found in ordinary wild rabbits. One of our original stock 

 of rabbits (9 431) , a Belgian hare, was of this sort. In a variety of crosses she 

 produced only gray offspring. 



TABLE 31. --Matings and young of 9 431, the Belgian hare. 



The matings with J 56 and 3 8 indicate that she did not carry albinism as 

 a recessive character; the mating with the yellow rabbit shows that she did not 

 carry yellow as a recessive character. The yellow rabbit in question was found 

 by other tests to be heterozygous in the pattern factor A. Consequently the 

 Belgian hare was almost certainly homozygous in that factor; otherwise half 

 the young produced in this mating should have been black instead of gray. 



(2) A second sort of gray rabbit produces (when mated with animals like 

 itself) gray offspring and black ones, but produces none of other color varieties 

 in any kind of mating. It differs from variety i only in regard to the factor 

 A, in which it is heterozygous (single). Its zygotic formula accordingly is 

 B,Br 2 E 2 AC 2 I 2 U 2 Y 2 . In half its gametes the A factor is transmitted along with 

 all the other 7 factors; in half its gametes the factor A alone is wanting. Gray 



