SEX-LINKED LETHALS IN DROSOPHILA 107 



Second lethal and eosin 



The females of lot e, table 10, which gave a ratio of 116:46, 

 were bred to eosin miniature males. As shown in table 19, 

 fourteen of the females gave a 1 :1 ratio, and nine a 2:1 (or higher) 

 ratio. In the latter (2:1) class the double cross-over is the red 

 long male. Two of these that appear must be due to a double 

 cross-over. It is just possible, of course, that contamination 

 may have occurred because these two males appeared in the 

 same bottle and on the same day. 



WMI3 



a e I 



wmL3 



WmLj 



WML3 



VVml3 



W ^ L3 



Figure D 



The females of another lot, in table 10, viz., lot n with a ratio 

 of 58:20, were alsb bred to miniature eosin males. The results 

 shown in table 20 are strikingly different from any others so far ob- 

 tained. The second lethal no longer appears to be present, yet in 

 about half the cases the ratio is near 2:1. The question arises 

 whether a new lethal has appeared, or whether we have in this 

 set simply separated from the second lethal the other factor or 

 factors that when combined with the second lethal gave the 

 high 3:1 ratios. 



No more light is thrown on this matter by the further history 

 of this series. One lot only, viz., No. 39, seemed to give a 3:1 



