w 



w 



fi^ 



n 



\^ 



Fig. 74. Confirmation of Theory of Sex-linked Inheritance 



The assumption that eye pigment is inherited among fruit flies as it is because the 

 determiner is associated with the X chromosome is confirmed by crossing a white- 

 eyed female with a red-eyed male. According to the theory the factor or determiner 

 W would be carried by the single X chromosome of the male. Instead of all of the 

 Fi generation having red eyes, only the females have, since the males derived their 

 X chromosomes from the white-eyed (recessive) mother. In the following genera- 

 tion (F ) red and white eyes appear equally in both sexes. The red-eyed male is 

 always " hybrid " for eye color, according to this theory. Consequently the F^ has 

 only red-eyed females and white-eyed males, just the reverse of the parental characters. 

 From Morgan, The Physical Basis of Heredity, published by J. B. Lippincott 

 Company. 



