COLOR 



61 



not heterozygous in C. The matings with males 402, 1340, and 248 

 show that she was homozygous in E. 



TABLE 40. Matings and young of blue-gray 9 656. 



Female 1437 was either of variety 6 or else of variety 8, i. e., she was 

 known to be heterozygous in E and in A, but was insufficiently tested as 

 regards C. Mated with blue <? 1434 she produced 2 blue-gray and i pale 

 sooty young and i pigmented animal of uncertain character. 



BLACK. 



Black rabbits, as we have already observed, differ from gray ones only 

 in the factor A, which they lack completely. 16 different zygotic com- 

 binations are theoretically possible among them. 



(1) Black producing nothing but black; formula, B 2 Br 2 E 2 C 2 I 2 U 2 Y 2 (compare 



diagram, p. 52). 



(2) Black producing black, and white; formula, B2Br 2 E 2 CI 2 U 2 Y 2 . 



(3) Black producing black, and sooty; formula, B 2 Br 2 E(R)C 2 I 2 U 2 Y 2 . 



(4) Black producing black, sooty, and white; formula, B 2 Br 2 E(R)CI 2 U 2 Y 2 . 



(5) Black producing black, and blue; formula, B 2 Br 2 E 2 C 2 I(D)U 2 Y 2 . 



(6) Black producing black, blue, and white; formula, B 2 Br 2 E 2 CI(D)U 2 Y 2 . 



(7) Black producing black, blue, sooty, and pale sooty; formula, 



B 2 Br 2 E(R)C 2 I(D)U 2 Y 2 . 



(8) Black producing black, blue, sooty, pale sooty, and white; formula, 



B 2 Br 2 E(R)CI(D)U 2 Y 2 . 



The 8 remaining varieties would be identical with these 8, except that 

 they would be heterozygous as regards U, viz, U(S) instead of U. Con- 

 sequently they would produce spotted as well as self-pigmented young. 



All the black rabbits (with one exception) which we have used for breed- 

 ing purposes were produced in the course of our experiments from animals 

 of other color varieties. All were in one or more respects heterozygous, 

 except possibly the recently purchased black rabbit, not yet fully tested, 

 but apparently homozygous in all particulars and so of variety i. Hurst 

 (105) obtained rabbits of variety 2, but we do not happen to have had any 

 of this variety, nor of variety 3. 



Variety 4 is represented hi a modified form in our rabbits 104, 105, 167, 

 247, and 255. The modification consists in this: the albino offspring are, 

 at least in part, of the Himalayan type, having pigmented extremities. 



