Case I. White-eyed male x Red-eyed female. 



The male gametes are of two kinds, viz. rX and Y, 

 while the female gametes are all RX. The matings may, 

 then, be represented as follows : — 



rX 



Female 

 Gametes 



fRX 



RX 



male gametes 



all red-eyed 



The diagram of the Fa generation is — 



RX Y = male Gametes 



fRX 



Female 

 Gametes - 



rX 



50% red-eyed females 

 25% red-eyed males. 

 25% white-eyed males. 

 Ratio — 3 red to 1 white 



Case II. White-eyed male x Fi red-eyed female {Hete- 

 rozygous). 



The male gametes are of two kinds: rX and Y, while 

 the female gametes ^e RX and rX. The matings may be 

 represented as follows: — 



rX 



Female 

 Gametes 



fRX 



rX'' 



Red-eyed 

 female 



White-eyed 

 female 



Red-eyed 

 male 



White-eyed 

 male 



= male gametes 



25% red-eyed females 

 25% red-eyed males 

 25% white-eyed females 

 25% white-eyed males. 



Case III. Red-eyed male x white-eyed female. 



The male gametes are RX and Y, and the female game- 

 tes rX and rX. 



RX 



Female 

 Gametes 



rX 

 rX 



= male gametes 



red-eyed 

 females and 



white-eyed 

 males 



Showing that the red-eyed male parent is heterozygous 

 for color. 



113 



