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TEE AMERICAN NATURALIST 



[Vol. LVI 



has been to preserve the black in the hackles, wings and 

 tails and to heighten the contrast with the white body 

 by selecting against grayness or mealiness in the body 

 feathers. Two principal processes were apparently in- 

 volved in the production of buff and Columbian vari- 

 eties ; a discontinuous change or. mutation producing the 

 chief difference, and the accumulation by selection of 

 minor factors producing the minor changes. It is im- 

 possible to say whether the buff and Columbian varieties 

 which exist at the present time in the principal breeds 

 were derived from these original types by crossing or 

 whether the principal mutation and the minor changes 

 and selection have recurred in the different breeds. The 

 probabilities are in favor of the first alternative. 



Summary 



1. The Columbian plumage coloration in domestic fowls 

 is distinguished from buff coloration by the presence of 

 a gene S which determines the restriction or inhibition 

 of buff pigments from the feathers. This gene is sex- 

 linked, and dominant over its allelomorph s, which per- 

 mits the development of buff pigment. 



2. Fowls with the Columbian coloration do not differ 

 from buff fowls in any single gene governing the develop- 

 ment of black pigment. Multiple genes appear to de- 

 termine the difference in the amount of black pigment 

 developed. 



3. Columbian and buff fowls are genetically alike in 

 plumage pattern, that is, in the ability to develop black 

 pigment in the feathers of certain areas (hackle, wing 

 and tail feathers). 



4. The buff coloration appears to have diverged from 

 the Columbian coloration, or the reverse, by a single gene 

 mutation affecting the development or inhibition of buff 

 pigment; and by the accumulation through artificial se- 

 lection of multiple genes for the development of black 

 pigment in the Columbian varieties of fowls, and by the 

 reverse selection in most buff varieties. 



