44 Genetic Studies in Poultry 



obtained satisfactory evidence. It is however clear that it is not due 

 to the factors that influence the length of the hackles in normal breeds. 

 Intermediates with a marked tendency to normal cock feathering can 

 be bred from short-feathered races such as A seels and Game Bantams, 

 as well as from breeds relatively long in the feather such as the Brown 

 Leghorn. Further, the various gi-ades of intermediates together with 

 full henny birds can be bred from the same mating, where all of them 

 are heterozygous for the henny factor. Whether the homozygous cock 

 can be an intermediate we cannot at present say, for, as we have already 

 stated above, we have not yet succeeded in identifying such a bird. 



Colour of Intertnediates. 



In our account we have restricted the term " intermediate " to birds 

 differing from the normal cock in the structure of those feathers in 

 which the sexes of normal breeds differ from one another. The structural 

 difference is due to the elongation of the rachis and distal barbs, and to 

 the loss of the barbules on the barbs. Proximally, of course, even in a 

 truly male saddle-hackle, barbules are present and are furnished with 

 barbicels. 



When an intermediate of a pronounced cock-like type becomes henny, 

 a marked difference in the general colour of the bird results, as well as 

 in the form of the feathers. The principal factor in this change is the 

 deposition of melanic pigment in the feather. It is well exemplified by 

 the feathers shewn on PI. VII, figs. 1 and 2. The deposition of the melanic 

 pigment on the assumption of the henny plumage brings about a very 

 great difference in the general appearance, and there arises the in- 

 teresting question whether the henny cock assumes the colour as well 

 as the plumage structure of the hen that corresponds genetically to 

 him. That the colour correspondence as well as the structural one may 

 in some cases be very close is shewn by Morgan's experiments in the 

 castration of Sebright Bantams (cf Morgan, 1919, PI. I, figs. 3 and 4). 

 If we assume that the castrated bird represents the appearance that the 

 cock of this breed would have if the henny factor were not present in 

 him, then we must suppose that the " hennification " of such a male 

 would result in a cock which in colour, as well as in plumage structure, 

 was practically identical with the hen. There are many breeds in which 

 the cock differs markedly from the hen in colour in those feathers only 

 in which there is a structural difference in the sexes. This is naturally 

 true of self-coloured breeds such as blacks, buffs, and whites, as well as 



