1 64 Gene H and Testosterone in the Fowl 



which separately and independently will give the same effect remains to be 

 determined. Capons of the formula hh respond in the same way to thyroxin 

 and estrone but not to testosterone, and this suggests once again that it is not 

 so much the hormone as the way in which the tissues have come to respond to 

 it that is of fundamental importance. In the case under consideration one 

 simple genetic alteration— a change in the character or position of a single 

 gene— suffices to convert tissues of the feather follicle from a condition of 

 sensitivity to estrone and indifference to testosterone to one in which they 

 are apparently insensible to the difference between these two hormones and 

 respond equally to both of them. 



In this paper the convention has been followed of considering the deposi- 

 tion of pigment as if it were a passive phenomenon, but of late it has been 

 shown that the pigmentophores have a great deal of autonomy and may play a 

 definite and largely independent role in the determination of pattern (Willier 

 and Rawles;^^ Danforth^*). Studies on plumage have paid little attention to the 

 question of whether or not gene H affects the pigmentoblasts directly, or only 

 alters the character of the "parade ground" on which they may deploy. It may 

 be remarked in passing that in plate 1, figure 3, here, and in many figures by 

 Parkes and others, both the laced henny and the striped cocky feathers are 

 shown to be characterized by the alignment of black pigmentophores along the 

 most distal barbules in the vane wherever those barbules may be. This sug- 

 gests that the underlying factor may be related more to pigmentophore orienta- 

 tion than to mere pigment deposition, but this is a problem yet to be solved. 



In conclusion it may be pointed out that thus far we seem to have gotten no 

 inkling as to the underlying basis for sexual differences in plumage, but we 

 have succeeded in gathering considerable information about some of the 

 factors which condition the appearance of one or the other of the alternative 

 types. That the whole situation may be fundamentally altered by a simple 

 cytological change is apparent in the effects produced by gene H. 



REFERENCES 



1. Punnett, R. C: Jl. Genet. 35:129, 1937. 



2. Tegetmeier, W. B.: The Poultry Book (London: 1873). 



3. Article on "Bantam," in Encyclopedia Americana, III (1941 ed.; New York: 1941), 215. 



4. Dixon, E. S.: Ornamental and Domestic Poultry (London: 1848). 



5. Pezard, A.; Sand, K., and Caridroit, F.: Archs. de biol. 36:541, 1926. 



6. Greenwood, A. W., and Blyth, J. S. S.: JL Genet. 36:53, 1938. 



7. Domm, L. V.: in Sex and Internal Secretions, ed. by E. Allen (2d ed.; Baltimore: 1939), 227. 



8. Goodale, H. D.: Amer. Naturlst. 47: 159, 1913. 



9. Morgan, T. H.: Proc. Soc. Exper. Biol. & Med. 13:31, 1915. 



10. Morgan, T. H.: Proc. Soc. Exper. Biol. & Med. 15:3, 1917. 



1 1. Morgan, T. H.: Carnegie Instn. Washington, Publn. no. 285, 1919. 



12. Nonidez, J. F.: Jl. Anat. 31:109, 1922. 



13. Nonidez, J. F.: Jl. Anat. 34:359, 1924. 



14. Roxas, H. A.: Jl. Exper. Zool. 46:63, 1927. 



15. Danforth, C. H., and Foster, F.: Proc. Soc. Exper. Biol. &: Med. 25:75, 1927. 



