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. 







J^st.r'erits 



J^J 





jrz 





Ko 2u o ^'''^f''''^^ '"'■''^'^ ""^ ^'^^- 40. Upper line, black cock and 



barred hen. Second line, F,, barred cock and black hen. Third line F-, 



Wnll --r ^S^ 'r^' "^^^'^ '^^^^ ^"^ ^^"- (C^ts from "Reliable Poultry 

 Journal. ) Fx and Ft correct for color pattern only. 



