64 



The Journal of Heredity 



WHITE LONGWOOL EWES AND THEIR BLACK LAMBS 



When longwool ewes are bred to full-blooded Karakul rams, the lambs are always black, and 

 have wool of the popular "Persian lamb" type. The geneticist accounts for this fact by saying 

 that black wool, with its correlated desirable factors of tight curl, density, and lustre is dominant 

 over white, slightly curled wool. Black hybrid ewes of this type are in some cases worth as much 

 as $250 each. (Fig. 7.) 



On crossing, union occurs between 

 gametes (BR), (Br), and (br) forming a 

 heterozygote of the combination 

 (BbRr) or (Bbrr). Both these zygote 

 forms should be phenotypically black in 

 color. In the case of the two chocolate 

 colored lambs produced in 1912 and 

 1913 they could just as logically, from a 

 genetic standpoint, have been called 

 light colored Ijlacks, in fact they were 

 more black than red. As to why these 

 particular two individuals should be 

 light colored and not all others with the 

 same zygotic combinations, can only 

 be explained by assuming that the 

 particular black factor in the form 

 (BbRr) in their case failed to give 

 complete dominance. The results ob- 

 tained later when the black P^i ewes 



w^ere crossed further strengthen the 

 above assumption. 



In 1914 the Fi ewes were bred to an 

 imported full-blood Karakul ram 

 named Pultava. This ram, it was 

 naturally supposed, would give com- 

 plete dominance of black fleece, to- 

 gether with its correlated desirable 

 factors of tight curl, density and 

 bright luster. Fifty-six Fi black ewes 

 bred to Pultava in 1914 produced 41 

 blacks, 11 red or spotted, and 11 whites. 

 In 1915 he was bred to 100 black Fi 

 ewes, as the 1913 ewe lambs were now 

 ready to breed, and produced 80 blacks, 

 17 red or spotted, and 14 whites. The 

 two years then give the produce of 156 

 Fi ewes, with a combined total of 174 

 lambs of which 121 were blacks, 28 red 



