THE MECHANISM OF SEX-DETERMINATION 71 



the female that produces two kinds of eggs ; she is 

 heterozygous for a sex factor while the male produces 

 only one kind of spermatozoon. 



; ,sk 



Fig. 41. — Reciprocal cross of Fig. 40. Upper line, black cock and 

 barred hen. Second line, fr\, barred cock and black hen. Third line, Fi, 

 barred hen and cock, black cock and hen. (Cuts from " Reliable Poultry 

 Journal.") F\ and F2 correct for color pattern only. 



