SEX-LINKED LETHALS IN DROSOPHILA 



101 



From lot 16 of table 11 several virgin long-red females were 

 mated in pairs to white miniatm-e males. Their offspring are 

 shown in table 12. Each pair shows in its offspring that the 

 second lethal was present in the long winged red mother. A 

 further generation was reared in pairs from red females of lots 

 b and c of table 12. The offspring recorded in tables 13 and 14 

 show that the 2:1 sex-ratio continues. 



Returning to table 11 there are records of two lots taken 

 respectively from No. 4 and No. 5. The offspring from these 

 pairs are here shown in tables 15 a and 15 b. Both show that 

 lethal II is present as indicated by the absence (or rarity) of the 

 red long male^. 



Before examining the preceding tables 10 to 15 in detail it 

 may be helpful to have in mind certain theoretical relations. 

 The location of factors for white (w) and for miniature (m) 

 have been already determined. If we are dealing here with a 

 lethal factor, it is essential to determine its position in relation 

 to white and to miniature. For reasons that will appear later 

 it is here assumed that this lethal lies between white and minia- 

 ture (fig. C). 



TABLE 14 

 (From No. c of table 12) 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 17, NO. 1 



