72 INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



color enzyme, as well as the Jungle pattern and the supermelanic coat. 

 But all of these are rendered invisible by the graying factor W. The super- 

 xanthic factor is missing. 



2. BLACK. 



The uniform black birds that I have studied are of several sorts. The 

 Black Minorca and White-faced Black Spanish have the gametic formula 

 CJNwx. Owing to the absence of the graying factor and the presence of 

 the color factor these appear as pigmented birds, but the supermelanic 

 coat, N, obscures the Jungle coloration, so that the bird appears entirely 

 black. Nevertheless the black is not of uniform quality, but just those 

 parts of the feathers of the wing, back, hackle, saddle, and breast that are 

 red in the Jungle fowl are of an iridescent black, while the portion that is 

 not red in the Jungle is of a dead black. 



The Black Cochin has the gametic formula CINwx. This differs from 

 the formula of the Minorca only in this respect: the Jungle pattern is 

 present, but not the pigmentation that is usually associated with it. 



The Black Game ("Black Devil") that I used in a few experiments 

 seemed to have the same gametic formula as the Minorca, only the super- 

 melanic coat was less dense. 



3. BUFF. 



For this color I used Buff Cochins, the original buff race. The gametic 

 formula of this race proves to be CjnwX — the Jungle-fowl pattern being 

 absent. 



B. EVIDENCE, 



The evidence for the gametic interpretations of the self-colored fowl 

 is derived from hybridizations. It will now be presented in detail. 



1. SILKIE X MINORCA (OR SPANISH). 

 (Plates 3 to 6.) 



By hypothesis this cross is between cJnwx and CJNwx. The first 

 generation should give the zygotic formula CcJ^Nnw^x^, or, more simply, 

 CcJ^Nn. This formula resembles closely that for the Minorca; but it differs 

 in this important respect, that the coloring factor and the supermelanic 

 factor are both heterozygous, and hence diluted. 



Actually I found, as Darwin (1876) did, that the chicks of this first 

 hybrid generation were all wholly black. In this respect they differed 

 markedly from the chicks of the Silkie, which are pure white, and also from 

 the chicks of the Minorca, which are prevaiUngly black, but have white 

 belly and outer primaries. The white in the young chicks of Minorcas is 

 extremely variable in amount, but never wholly absent; in time, as the bird 

 grows older, it is replaced by black, so that the adult male and female 

 Minorcas have a wholly black plumage. The reason for the precocious 

 development of black pigment over the belly and primaries of the hybrid 

 chicks is probably the presence of an extension factor (c/. Castle, 1909) 



