MORGAN AND GOODALE, INHERITANCE IN POULTRY 131 



Color of Legs. — It has been stated by Bateson and by Pearl that yel- 

 low and black shanks in certain breeds of poultry show "sex-linked" 

 inheritance. This is not apparent in the Langshan-Dominique crosses, ex- 

 cept in so far as black shanks accompany black color of feathers. For ex- 

 ample, in the F 2 generation, there are recorded 13 black birds with black 

 legs. Of these, 5 were deep yellow on the under side of the feet. In 

 addition, there was one male that had yellow shanks and yellow under 

 the feet. There were recorded 12 barred F 2 chicks with yellow shanks. 

 Of these 12 birds, 4 are recorded as having very pale yellow or whitish 

 legs. It would appear from this case that black and yellow shanks 

 accompany black and barred plumage, at least as a rule. 



In the back cross of the F x barred male to the parent Dominique hens, 

 in which there were barred males and females and only black females, 

 all 1 of the black birds had black legs, while all 12 barred birds had 

 yellow or pale legs. Among these 12 barred birds, there were 5 with 

 pale legs; in 2 of these and in one yellow, there were spots of black or 

 dark color, at least on the tarsus. 



These- rather meager figures, as far as they go, show that shank char- 

 acter and color of plumage go together, and that black shanks and yellow 

 shanks are only an accompaniment to sex-linked inheritance of plumage. 

 The data are manifestly few, however, and it may well happen that the 

 two characters may appear disassociated. 



Color of Bill. — The color of the bill seems to run a parallel course. 

 Full records for the back cross given above were kept. Here, 13 barred 

 birds had yellow bills and 5 black hens had black bills, but one of the 

 latter had much yellow on it, and two of the former had black : one was 

 black with yellow tip and the other was yellow and black. There is much 

 variability in the color of the bill, and the above statements are insuffi- 

 cient to warrant any generalizations. 



Theoretical Considerations 



The current formula for sex inheritance in fowls represents the female 

 as heterozygous for sex, F-O, and the male homozygous, O-O. If F is 

 identified with a special chromosome connected with sex determination, 

 the formula calls for one more chromosome in the female than in the 

 male. At present, evidence on this point is conflicting and insufficient. 

 It is true that Guyer has described two kinds of spermatozoa in the male, 

 one with an X and one without. If this X is the same as in other ani- 

 mals, then the spermatozoa containing it must be female producing, and 

 the female should contain one more chromosome than the male. This 

 means that the male and not the female is heterozygous for sex. The 



