The Germ Cells of Dtptera 371 



of 1906-07, Drosophila was bred in the laboratory on two kinds of 

 food, grapes and bananas. As the flies were dissected for the 

 cytological work, a record was kept of the numbers of each sex; 

 1 55 1 were so recorded. Of these 759, or 48.94 per cent were 

 males; 792, or 51.06 per cent females. The records of the grape- 

 fed and the banana-fed flies were kept separately. The total 

 number of grape-fed flies dissected between November i and 

 March 19 was 787, 404 or 51.33 per cent being males, and 383 or 

 48.67 per cent females. The banana-fed flies between October 

 30 and December 3 numbered 764, 355 or 46.47 per cent males, 

 and 409 or 53.53 per cent females. In the total number there 

 were 2.02 per cent more females than males, in the grape-fed 

 2.66 per cent more males than females, and in the banana-fed 

 7.06 per cent more ferhales than males. These differences are 

 probably not significant, but if sex is a Mendelian character, the 

 numbers for the two sexes should of course be equal unless food 

 produces some discriminating effect on the development of either 

 individuals or eggs of the different sexes. It has always been a 

 noticeable fact that the banana-fed flies were larger and more 

 robust than those fed on grapes; this however applies to both 

 sexes. In mass cultures it is not possible to tell whether failure 

 of many of one sex or the other to reach the adult stage in differ- 

 ent cultures might account for the discrepancies in numbers 

 observed with the two kinds of food. 



Castle and his co-workers ('06 p. 772) found the sexes about 

 equal in three families of the sixth inbred generation of a grape- 

 fed series, and the remarks which follow the table indicate that 

 they regard the normal proportion as near equality. 



Monkhaus' results on sex in Drosophila seem not yet to be in 

 print, except for a brief report in the Year Book of the Carnegie 

 Institution. 



An attempt was made to ascertain the normal proportion of the 

 sexes for the adults of Musca domestica. When caught by hand 

 58.33 per cent were females, but when a wire trap baited with 

 sugar or molasses was used, only 46.53 per cent were females. 

 The results need no comment. 



Cuenot states that the normal proportion of males to females 



