R. C. PUNNETT AND THE LATE MaJOR P. G. BaILEY 51 



moulted out henny. In his case however the development of inter- 

 mediate feathers was much less marked, and the tendency to develop 

 them may have been overcome by the time the moulting season arrived. 

 The whole matter remains obscure. It is clear that much more experi- 

 mental work must be undertaken before we can hope to understand it. 



General Discussion. 



Granted then that hen-feathering behaves in heredity as though 

 it 'were dependent upon a single factor ; further, that its manifestation 

 depends upon the presence of the gonad, we may ask whether we can 

 associate the factor with any particular tissue. This Morgan claims to 

 have done, regarding the so-called luteal cells of the ovary as the 

 seat of a hormone which brings about the development of feathers 

 belonging to the hen type. He states that these luteal cells are also 

 found in the testis of henny, though not in those of normal cocks. If 

 this is so, it is plausible to identify the henny hormone with a specific 

 tissue. The identification is supported by Goodale's work on the Brown 

 Leghorn hen, as well as by the work of Pezard, castration in either case 

 leading to the assumption of the normal cock plumage. It seems clear 

 that henny feathering, in either sex, is due to a hormone produced in 

 the gonad : and that something necessary for the production of this 

 hormone can be represented by a factor in gametogenesis. So far as we 

 can see, there is no reason for regarding a hormone that leads to hen- 

 feathering in the female as different from one leading to hen-feathering 

 in the male. Each produces a similar effect, and the effect of castration 

 is in each case similar. We are led therefore to infer that the factor 

 transmitted is identical in the two cases. If this is so, it is clear that 

 the precise mode of transmission in the two cases is different. 



In normal breeds we must suppose the transmission to be sex-linked. 

 The female we may regard as heterozygous for the henny factor as well 

 as for sex. To her daughters she transmits both the factor for female- 

 ness and that for hen-feathering : to her sons, neither. In other words 

 there is complete linkage between these two flxctors in the gameto- 

 genesis of the normal hen ; and if we had no knowledge of henny cocks, 

 we might have considered the two characters as due to one and the 

 same factor. There is however a point of difference between this and 

 the other sex-linked cases hitherto described in poultry. In all of these 

 the heterozygous hen transmits the recessive character to her daughters, 

 the dominant to her sons. We may recall the barring of the Plymouth 

 Rock, silver plumage as opposed to gold, the inhibitor for the pigmen- 



4—2 



