462 



AUSTIN RALPH MIDDLETON 



Experiment 1-A, while favorable to the production of an heredi- 

 tary effect through selection, was to show that opposite selec- 

 tion must continue for a much longer period before the nature 

 of the result can be established beyond controversy. 



Experiment 1, part 2. Continued opposite selection, Decem- 

 ber 4 to December 23, 1913. 



While Experiment 1-A was in progress certain fast and slow 

 lines of Experiment 1, part 1, were kept under direct selection 

 as a precaution against the possibility that selection in that 

 experiment had not yet produced heritable differences in the 

 fission rate. For this purpose fast lines 6, 30, 43, 45, 60, 73, 

 76, 78 and 100 and slow lines 3, 4, 9, 41, 53, 71 and 85 were 

 chosen. During the first of these two ten-day periods the ani- 

 mals were transferred to fresh slides every twenty-four hours 

 and during the second ten-day period, every forty-eight hours. 

 The actual number of generations produced by each of these 

 lines, during the two ten-day periods is shown in table 4. 



TABLE 4 



Expermient 1, Part 2: Actual number of generations and selections per line per 

 ten-day period, with the excess of generations in favor of the 'fast.' Direct selec- 

 tion of the fourth and fifth ten-day periods of Experiment 1. 



LINES NUMBER 



FAST 

 SLOW 



Fourth 10-day Period: 

 Fast: 



Selections 



Generations 



Slow: 



Selections 



Generations 



Excess in favor of ' fast' 

 Fifth 10-day Period : 

 Fast: 



Selections 



Generations 



Slow: 



Selections 



Generations 



Excess in favor of ' fast' 



AVERAGES 



17.14 



14.71 

 2.43 



9.28 



5.71 

 3.57 



