THE MECHANISM OF SEX-DETERMINATION 65 



Other combinations give results that are predictable 

 from those just cited. For instance, if the Fi red-eyed 

 female from either of the preceding crosses is mated to 

 a white-eyed male, she produces red-eyed males and 

 females, and white-eyed males and females, as shown in 



ct 



X 



XX 





XI If 



Fig. 36. — Reciprocal cross of Fig. 35. Parents, white-eyed ? and 



red-eyed $, (criss-cross inheritance). F u red-eyed <?v white-eyed $. 



F2, red-eyed 9 and $ ; white-eyed 9 and $ . To right, sex chromo- 

 somes (as in Fig. 35). 



Fig. 37 (upper two lines). If the F x red-eyed male 

 from the first cross (Fig. 35) is bred to a white-eyed 

 female, he will produce red-eyed daughters and white- 

 eyed sons. Fig. 37 (lower two lines). 



The same relations may next be illustrated by an- 

 other sex-linked character. 



