A PHYSIOLOGICAL CHARACTER. 63 



means (340 and 394 seconds) differing by -54 23.39 seconds, a 

 result out of accord with that for the means for the complete data 

 for this year and with that for the test series now to be considered. 



The test series conducted in May 1914 consisted of 23 broods 

 from each strain (320 individuals of the plus and 331 individuals of 

 the minus strain). Of the 23 pairs of broods, 17 broods from the plus 

 strain had the higher reaction-time, while the minus brood had the 

 higher reaction-time in only 6 cases. The reaction-time means for 

 the entire test series were 520.8 and 463.6 seconds. The difference 

 was +57.2 14.9 seconds, a difference 3.83 times the probable error 

 (table 25). 



For the final period (11 months) of the experiment with Line 

 719, the mean for the plus strain was 364.2 seconds, for the minus 

 strain 345.0 seconds. The difference was +19.2 12.5 seconds, a 

 difference only 1.53 times the probable error. The ten same-day 

 broods gave means of 351 and 378 seconds, and a difference of 27 

 seconds; again the same-day-brood data is out of accord with the 

 data for the year-period. A test series conducted during November 

 1914 and consisting of nearly 1,000 individuals from each of the 

 strains gave means of 310.9 and 290.6 seconds and a difference of 

 +20.3 6.3 seconds (table 25). This difference, while small, is 3.22 

 times the statistical probable error. 



The course of the curves (figure 8c) throughout is rather irregu- 

 lar, particularly for the plus strain, but the marked tendency for the 

 curve for the plus strain to be higher than that for the minus strain 

 is suggestive of a real difference in reactiveness between these two 

 strains, with the minus strain generally, though slightly, the more 

 reactive. In addition to the data for the entire course of the experi- 

 ment when considered by longer periods, the two test series, and a 

 minor portion of the data for the same-day broods, likewise tend to 

 indicate that the minus strain was the more reactive. But the 

 differences are less pronounced during the last year of the experiment 

 than during the earlier two years. The minus strain was more re- 

 active than the plus strain by only 19 seconds (a difference not of 

 statistical value) during the last year-period. The differences for the 

 earlier two years were 46 and 43 seconds and were 3.81 and 3.28 

 times their probable errors. However, the large test series conducted 

 during this last year-period indicated that the minus strain was the 

 more reactive by 20.3 seconds (a difference very near that for the 

 last year's selection data) and because of the large number of indi- 

 viduals used in this series and the consequently smaller probable 

 error this difference was 3.22 times the probable error. 



The data for Line 719 as a whole and particularly the data of 

 the 2 test series are very suggestive of a genetic difference in oppo- 

 sition to selection between the two strains of Line 719, in spite of the 

 lack of confirmation from most of the same-day-brood data and the 



