A PHYSIOLOGICAL CHARACTER. 39 



is obviously due to environmental factors. The data for the first 4 

 months previous to August 1, 1912, may be passed over with slight 

 consideration, for (as stated above) the methods of handhng the 

 material were not sufficiently standardized at first. These first 2 

 two-month^ periods show rather widely different averages (see tables 

 6 and 7 and figure 2c), but from this time on less violent fluctuations 

 in average reaction -times are encountered, except for very wide 

 fluctuations in the average of the minus strain during the latter half 

 of 1915, and an unusual upshoot in the plus strain during the last 4 

 months of the experiment. ^ 



For the year, August 1, 1912-July 31, 1913, the mean reaction- 

 time for the plus strain was 260.2 seconds (251 individual reaction- 

 time records; see table 7) and for the minus strain 297.5 seconds 

 (217 individual reaction-time records). The minus-strain mean was 



— 37.3 seconds greater than that for the plus strain. The difference 

 was 3.2 times the statistical probable error (table 7). This large 

 difference is due, of course, to the difference obtaining for the first 

 6 months of this year-period. This six-month period is discussed 

 later. In the latter half of the year there was not a consistency in 

 reaction-time differences, though on the average the plus was slightly 

 the more reactive. The *' same-day" broods for the year-period have 

 a mean reaction- time for the minus strain only 0.8 second greater 

 than for the plus strain (table 8). 



For the year, August 1913-July 1914, the curves show that the 

 two strains differ little in mean reaction-time (plus mean 371.8 

 seconds with 361 individual reaction-times; minus mean 371.3 

 seconds with 304 individual reaction-times; see table 7) and in relative 

 vigor (see figure 2b). For the entire year the mean reaction-times 

 differ by only -|-0.5 second and the same-day broods by only —12,3 

 seconds (table 8). Two test series were conducted during this 

 period. One in August 1913 consisted of 529 individuals in the plus 

 strain and 467 individuals in the minus strain. The mean reaction- 

 times were 522.2 seconds and 490.5 seconds for the plus and minus 

 strains respectively, a difference of -F31.7 seconds ±12.14 seconds. 

 This difference is 2.61 times the probable error. The second test 

 series, May 1914, consisted of 1,083 and 1,088 individuals and the 

 means were 501 and 562.8 seconds. The difference in seconds was 



— 61.8 ±8.88, a difference 6.96 times the probable error. The 

 results of these two test series are contradictory and judgment will 

 be reserved until the later data are considered. 



' The summaries of the data for the earlier portion of the experiments were made to include 

 the first 4 months. Summaries thereafter were made covering year periods. Summaries for the 

 lines later subjected to selection were made to conform to the summary periods already utilized 

 for the older lines. 



^ Actually this is only a trifle more than 3 months, as the selection was discontinued Septem- 

 ber 2, 1916. 



