100 



SELECTION IN CLADOCERA ON THE BASIS OF 



was 36.08 times its probable error. In every case in this test series 

 the plus brood had a lower reaction-time than the corresponding 

 minus brood. 



For the year August 19 14- July 1915 (43 generations and 472 

 individuals, and 44 generations and 507 individuals, respectively) 



Table 45. — Selection summary for Line 757. 



Table 46. — Same-day broods. Summary of data for Line 757. 



the mean reaction-times differed by —102.0 ±12.87 seconds (table 

 45). This is a difference 7.93 times the probable error. None of the 

 8 minus same-day broods had a reaction-time lower than that for 

 the corresponding plus brood. The mean reaction-time for these 



