124 ANNALS NEW YORK ACADEMY OF SCIENCES 



this may be, in F, the black birds again have black shanks, but the bot- 

 toms of their feet, which are usually incompletely covered by black, are 

 either gray or yellow. The allelomorphs involved, then, are gray versus 

 yellow (or Gray 2 , Yellow 2 , X, ISTo gray 2 , Yellow 2 ), the latter being re- 

 cessive to the former. Moreover, among the barred birds, only gray or 

 yellow shanks appear, or in other words, gray-shanked birds always have 

 gray soles, yellow shanked birds yellow soles, but black-shanked birds 

 may have either gray or } r ellow soles. 



Since, then, the black-shanked condition is due to an extension of the 

 general black color of the body, we need consider further only the rela- 

 tion of gray to yellow, the determinations being made, of course, only 

 on the bottoms of the feet and when the birds were several months old. 

 In F 1; there were only gray or pinkish gray feet, and, therefore, there is 

 no evidence that gray is sex-linked. Moreover, since no other color than 

 yellow appeared in F 2 , yellow is probably common to both Langshan and 

 Rocks, so that absence of gray in this case means yellow. In F 2 , not all 

 the adults were available for study, as the importance of foot color was 

 not realized until after many of the birds had been disposed of, but in 

 17 cases, 13 were gray and -1 yellow. The back mating of ¥ 1 gray male 

 to P x gray (Langshan) female gave 6 gray. The back mating of P x 

 yellow (Rock) male to ¥ 1 gray (black plumage) female gave 6 graj 7 to 2 

 yellow. These results indicate, then, that gray and yellow feet (or 

 shanks, leaving out of consideration the supermelanic coat) behave in 

 simple Menclelian fashion. 



We have suggested that black individuals have black shanks, because 

 a restriction factor is absent from these birds, so that the body color 

 spreads out as a self color over the shanks. Such a "restriction" factor 

 would be sex-linked. Is it, then, the same as the barring factor? If it 

 were a separate factor, we should expect that, in F 2 , a certain amount of 

 segregation would take place. This has not been observed, so that it 

 seems probable that the black shanks of the black birds are due to the 

 absence of the barring factor and the mottled shanks to its presence, 

 unless some "association" exists. Thus, the presence of the barring fac- 

 tor results in two (perhaps three) distinct somatic conditions, viz.: 

 barred feathers and mottled shanks, and, as a possible third, the gray 

 occipital spot of young chicks. In other words, we have two or more 

 unit characters resulting from the operation of a single factor. 



There are some considerations of a practical nature resulting from the 

 relations between shank color and sole color which should be mentioned. 

 If the black color covered the entire foot, we should be unable to deter- 

 mine what color underlay the black, except perhaps by long-continued 



