82 



SELECTION IN CLADOCERA ON THE BASIS OF 



For the second longer period the reaction-time means were 

 619.1 and 697.5 seconds. The difference was 78. 4 14. 7 seconds, 

 5.33 times the probable error. The 10 same-day broods gave averages 

 differing by only 6 24. 07 seconds. 



The data for the last longer period (August 1916 to the end of 

 the selection experiment in April 1917) gave as means 449.4 and 



2.00- 



1.50- 



1.00- 



.50- 



00 



750 - 



600 



450 - 



300 - 



150 - 



FIGURE 13. Line 796. 



A. Reproductive indices, actual values. 



B. Reproductive indices, superiority. 



C. Reaction-time curves. (The asterisk indicates a point 



established from insufficient data, only one brood.) 



393.7 seconds. The minus strain was the more reactive by 55. 7 19.1 

 seconds, 2.92 times the probable error. The same-day-brood 

 means (only 4 broods of each strain) differed by 220 seconds, the 

 minus strain being the more reactive. A test series conducted during 

 August 1916 consisted of 662 and 643 individuals in the two strains. 



