16 



C. B. DAVENPORT 



TABLE 11 



Fi (Dark Brahma cf X Brown Leghorn 9 ) X i^i (Dark Brahma cf X Brown 



Leghorn 9 ) 



For hackle lacing, W 



REMARKS 



Expectation; all cfc? and 50 per cent 

 females with white lacing; 50 per 

 cent 9 9 with red lacing 



For wing bar R, evident in males only 



Gametes. 

 F, 



Expectation; 50 per cent males with 

 red wing bar and 50 per cent with 

 white 



CONCLUSIONS 



The foregoing observations thus accord with the hypothesis 

 that the male carries two sex-chromosomes and the female one; 

 and that the determiners for certain secondary sex-characters are 

 centered in the sex-chromosomes. We have still to consider the 

 question: Are all sex-limited characters carried in the same 

 chromosome? This does not imply that the sex-limited charac- 

 ters of one variety shall always appear together. This is obviously 

 opposed to the facts, for in the first hybrid generation a white 

 hackle (Dark Brahma) and red wing-bar (Brown Leghorn) appear 

 together; and must always do so when the determiners for these 

 dominant traits are in the same zygote. In F2 from Brown Leg- 

 horn grandfathers two kinds of males are possible on the hy- 

 pothesis that the two sex-limited determiners are united, as in the 

 same chromosome: namely, with both red hackle and red wing 

 bar (consequently, quite like the pure bred Brown Leghorn) and 

 with red hackle and white wing-bar (the hybrid type) ; and these, 



