A PHYSIOLOGICAL CHARACTER. 



71 



in the fifty-fourth laboratory generation. Selections were continued 

 for 21 months, 75 and 74 generations in the plus and minus strains 

 respectively. The data will be found in tables 31 and 32 and in 

 figure 10c. 



The data for the first longer period (December 1914-July 1915) 

 consists of 29 and 28 broods from the two strains, there being 238 

 and 239 individuals. The mean reaction-times were 426 and 443 

 seconds. The difference is -17 ±19.5 seconds (table 31). There 



Table 32. — Same-day broods. Summary of data for Line 768. 



were a large number (17) of same-day broods for this period, for 

 which the mean reaction-times were 454 and 438 seconds. The dif- 

 ference is +16 seconds (table 32). 



For the year-period (August 1915-July 1916) there were 39 

 and 38 broods consisting of 376 and 294 individuals in the two 

 strains. The mean reaction-times were 315.7 and 328 seconds. The 

 difference is -12.3 ±12.4 seconds. There were only 4 same-day 

 broods, for which the mean reaction-times were 374 and 336 seconds. 

 The difference is +38 seconds. 



