A PHYSIOLOGICAL CHARACTER. 



79 



day broods averaged 617 and 479 seconds, the difference being 

 + 138=1=26.74 seconds. A test series conducted in June 1916, and 

 consisting of more than 1,300 individuals of each strain, gave a plus 

 mean of 615.4 seconds and a minus mean of 591.6 seconds. The 

 difference (+23. 8 8. 9 seconds) was 2.67 times the probable error. 

 Thus the data for this line to August 1916 indicates a signifi- 



2.00 

 1.50 

 1.00- 

 .50 



OO 



l- 



12-1 4-5 8-9 12-1 4-5 8-9 12-1 4 



1915 1916 '917 



750 



600 



300 



I50H 



f> 



12-1 



4-5 8-9 

 1915 



12-1 



4-5 



12-1 



1916 



/ 



4 

 1917 - 



FIGURE 12. Line 795. 



A. Reproductive indices, actual values. 



B. Reproductive indices, superiority. 



C. Reaction-time curves. 



cantly lower reactiveness on the part of the plus strain, a result op- 

 posite that of a selective effect. 



For the following and final 9 months of selection with this line 

 the plus strain averaged the more reactive; the means were 457.2 

 and 502 seconds, and the difference was 44. 8 17. 6 seconds, or 

 2.55 times the probable error. The 5 same-day broods gave as means 

 307 and 671 seconds. The minus same-day mean was more than 

 double that for the plus strain, the difference being 364 =t 33.38 

 seconds, 10.9 times the probable error. Of these 5 same-day broods, 



