R. C. PUNNBTT AND THE LATE MaJOR P. Gr. BaILEY 39 



Table I (p. 55) henny and normal cocks appear in approximately equal 

 numbers, the total containing 229 henny and 234 normal. We should 

 mention that although we have frequently bred from normal cocks born 

 of henny parents, we have never bred a henny bird in this way. Our 

 experiments suggest therefore that the difference between a henny and 

 a normal bird is a difference of a single factor throughout. 



It will be noticed that several of the earlier matings recorded in 

 Table I are between F^ birds. In 1912 we put up five pens of F^ birds, 

 since we wished to raise a considerable F., generation in connection with 

 the inheritance of weight. Two of these were headed by normal i^i cT cT > 

 and three by henny F^ </(/• Two of the latter turned out to have been 

 mated with F^%% {% 152 and $ 380 in Experiments 1 and 5) which 

 did not transmit the henny character to their sons, for when subse- 

 quently mated with normal cocks they gave only normal cock-feathered 

 sons. The remaining F^ henny cock {^ 203) was mated with F^ % 383, 

 and of the 19 (/•</ reared 16 were henny and 3 were cock-feathered. 

 This experiment is referred to in Table I as Exp. 43. $ 383 was 

 subsequently mated to a cock -feathered F^ ^ (398) and proved to be 

 heterozygous (Exp. 25). The mating between ^ 203 and % 383 was 

 a mating between two heterozygotes, and the proportions of henny and 

 normal </•(/ resulting was not far removed from the expected 3 : 1 ratio. 



Of the birds bred in Exp. 43 three henny c/c/ and eight pullets 

 were tested in order to ascertain whether any of them were homozygous 

 for the henny factor. Two of the henny (/</ were mated with normal 

 % % (Exps. 10 and 11) and both proved to be heterozygous. The third, 

 mated with a sister ( % 668), produced six henny and two normal sons^ 

 All three of the cocks tested proved to be heterozygous. Of the eight 

 pullets, two, mated to heterozygous cocks, gave both hennies and normals; 

 three, mated with normal cocks, gave both hennies and normals (Exps. 27, 

 28, 29) ; while the remaining three, mated to normal cocks, gave 9, 6, 

 and 11 normals respectively. None of the eight therefore could have 

 been homozygous. On ordinary expectation one of the three cocks and 

 two of the eight pullets should have been homozygous for the henny 

 factor. We failed however to find such a bird among the eleven that 

 were tested. 



Later on we made another attempt to find a homozygous bird. A 

 henny ^ (24/15) from Exp. 31 was mated with a sister ( % 95/15), who 

 was subsequently proved to be heterozygous in Exp. 40. This mating is 



1 This experiment is not included in the table as the hen used may have been hetero- 

 zygous. 



