354 DON C - WARREN. 



SELECTION EXPERIMENT I. (Bloomington Stock.) 



From a stock of flies collected in Bloomington, a virgin female 

 was selected and mated to a male from the same stock. From 

 the offspring of this pair of flies the high and low strains were 

 started. Before selection was begun, 2,936 flies were examined 

 for sex. The ratio was 1,456 males to 1,480 females, or I male 

 to i. 06 females. The ratio here is stated in just the reverse order 

 from the customary form but since Moenkhaus used the reverse 

 order, the ratios in the present discussion will be stated likewise 

 to make the two experiments more comparable. Table II. 

 gives the history of the origin of the high and low strains. 



TABLE II. 1 



Showing Origin of the "High" and "Low" Strains of the Bloomington Stock. 



206 (Original pair) 



I 



206 Ai 206 A2 206 As 



I I I I I I I 



15-30 84-74 63-52 108-130 93-100 152-140 91-121 

 Low High 



Tables III. and IV. give the history of the high and low strains. 

 There is no indication of the ratios having changed in the direc- 

 tion of the selection. In fact, in the high strain where there was 

 selection for a relatively high number of females, the totals show 

 a relatively lower number of females than in the low strain. 

 The totals for the high strain were 8,837 males to 8,942 females 

 or a ratio of I male to 1.012 females while in the low strain there 

 were 8,368 males to 9,091 females or a ratio of I male to 1.086 

 females. 



1 In all tables where two numbers are expressed with a dash between them, as 

 68-58, the number to the left of the dash always represents the male count and the 

 number to the right, the female count. 



