A PHYSIOLOGICAL CHARACTER. 83 



The means were 675.6 and 653.7 seconds. The difference was 

 +21.9 ±11.0 seconds, 1.99 times the probable error. 



Hence, for the first 2 longer periods the means for the entire 

 data gave higher reaction- times for the minus than for the plus 

 strain. These differences (—49.3 and —78.4 seconds) were 3.31 and 

 5.33 times their probable errors, but the lack of confirmation of 

 these differences from the same-day-brood data at once throws doubt 

 upon a real significance for these differences; while for the final long 

 period of the experiment with Line 796, the test series, the selection 

 data as a whole, and the same-day-brood data confirm each other in 

 indicating a greater reactiveness on the part of the minus strain. 



The data for this line would seem to present these points of 

 interest: a lack of selective effect, an effect of environmental in- 

 fluences upon reaction-time as indicated by the courses of the curves, 

 they following each other in a general way, and the lack of any marked 

 evidence of a relation between vigor and reaction-time in a case in 

 which the two strains differed extremely in vigor. This last point 

 may be worthy of a little further statement. 



The plus strain was very much the more vigorous during most 

 of the experiment, yet the differences in mean reaction- time were 

 not such as to indicate, everything considered, a significantly higher 

 reaction-time for the minus strain than for the plus strain. Indeed, 

 the same-day-brood data quite fail to confirm any significant dif- 

 ference in reaction-time between the two strains for any part of the 

 experiment. During the 3 two-month periods during which the differ- 

 ence in mean reproductive indices were greatest (figure 13b), the minus 

 strain was less reactive, but for 2 of the 3 other periods (in which the 

 inferiority in reproductive index for the minus strain was almost as 

 great) the minus strain was actually the more reactive. There were 

 altogether 9 periods of very low reproductive indices (about 1.00 or 

 lower) for the minus strain, and these were periods during which the 

 plus strain, with two exceptions, ran fairly high in vigor (reproductive 

 index over 1.50), and hence the difference in vigor was marked; yet 

 the minus strain, far from being markedly less reactive, was during 

 4 of these periods actually the more reactive. It was the less re- 

 active, however, during the other 5 periods and in 3 cases the differ- 

 ences were large. Though in general the reproductive index for the 

 minus strain of this line remained lower than that for the plus strain, 

 it regained a high level (1.7) soon after this divergence in reproductive 

 indices was most marked. 



Thus, while in both Lines 795 and 796 there was an apparent 

 cumulative effect of selection upon the vigor of the minus strain, 

 in both cases the effect was lost and the minus strain later attained 

 relatively high reproductive indices, although the method and pro- 

 cedure of selection were in no wise modified. 



