468 



AUSTIN EALPH MIDDLETON 



for eighty days, and the average difference per Hne per day had 

 increased from 0.267 generation for the first thirty days to 0.415 

 generation for the last thirty days of that period. To test the 

 permanence of this apparent effect of selection, to determine the 

 answer of our experiments to the question "Can we get from a 

 single genotype by selection two genotypes that differ charac- 



I I I I I I I I I I I I I I I I I Ill 



Fig. 5 Curve of the daily difference between the average number of gener- 

 ations per line produced by the fast set and the slow set during the sixth, seventh 

 and eighth ten-day periods of opposite selection in Experiment 1 (Exp. 1, part 

 3). The ordinates give the daily excess in favor of the fast-selected lines, the 

 abscissae give the days. 



teristically from each other under identical conditions; and that 

 retain these differences from generation to generation?" — the 

 lines were now subjected to the test of balanced selection. For 

 this purpose all the thirty fast and thirty slow lines which were 

 in progress at the close of Experiment 1, part 3, were continued. 

 In order to make the test thorough it was prolonged through 

 nine consecutive ten-day periods, or ten-days longer than the 



