No. 570] FACTORS GOVERNING DISTRIBUTION 353 



The points of interest to be noted in this table are as 

 follows : 



There are many supernumerary bristles in the flies of 

 this strain. 



The number of bristles added in the progeny of any 

 mating is very variable and has no consistent relation to 

 the visible character of the parents. 



Addition of bristles tends very much to favor the 

 females, reduction still affecting the males. 



Despite the high ratio of bristles added, there are 



