540 



MARY B. STARK 



linked factor close to the lethal factor in question a stock may 

 be obtained in which the lethal females may be selected with 

 great probability. For example: If a red eyed female carrying 

 a lethal is mated to a white eyed male half of her daughters will 

 have the factor for red and the factor for lethal in one X chromo- 

 some and the factor for white and the factor that is the normal 

 allelomorph of lethal in the other chromosome. If such a daugh- 



TABLE 7 

 13, 2, 8, 2 {foxir 1 : 1 ratios omitted) 



13, 2, 19, 6 {five 1:1 ratios omitted) 



13, 2, 19, 7 (three 1 : 1 ratios omitted) 



ter is mated to a white eyed male half of the female offspring will 

 be red eyed and half white eyed. The former getting their red 

 bearing chromosome from their mother will be the lethal bearing 

 females since the red bearing chromosome also carried the lethal 

 factor. By selecting the red eyed females, therefore, in each 

 succeeding generation and breeding them to white eyed males 

 the lethal stock can be maintained. 



Virgin females from numbers 13, 1, 11; 13, 1, 12; 13, 2, 1; 

 13, 2, 8; 13, 2, 19; of table 5 were mated to white eyed males. 

 The results are shown in table 6. 



