A PHYSIOLOGICAL CHARACTER. 



101 



minus broods was 200.0 ±21.11 seconds greater than that for the 

 plus broods (table 46). This difference was 9.46 times the large 

 probable error. There were rather striking fluctuations in the mean 

 reaction-times for both strains (and especially the minus) during 

 this year-period. 1 



While for 10 months of this year the minus strain, judged by 

 the reproductive index, was slightly, though very slightly, the more 



-2.00 



Figure 17. — Line 757. Reproductive vigor. 



A. Average number in first brood for the two strains. 



B. Average age of mother at time first brood was produced. 



C. Reproductive indices, actual values. 



vigorous of the two strains, it was the more reactive of the two 

 during the only two-month period of this year in which it was the 

 less vigorous of the two strains (see figures 18a and 18b). The mean 

 reaction-time for the minus strain was only 20 seconds greater than 

 that for the plus strain during the last two-month period of this year. 



1 These fluctuations in the means for the different two-month periods, so far as coincident in 

 the two strains, are due to the same environmental influences; and so far as they are not co- 

 incident they are presumably due to the somewhat differential handling of the two strains (see 

 pages 140-142). The material was handled with commendable care (mostly by an assistant) 

 during this year-period. 



