FISSION KATE OF STYLONYCHIA PITSTULATA 



493 



vitality and reproductive power; often changing the fission rate. 

 Conjugation was obtained among the selected individuals of this 

 third set of experiments, and its effect tested. 



Watch glass cultures were made in ^ per cent malted milk 

 from each of the thirty fast lines and the thirty slow lines. On 



iOt— 



/o - 



J L 



J L 



.-J" 



L«i 



^ I 



J I L 



I. 



J I 



Fig. li-c Polygon of the average number of generations i)er line per three- 

 day period produced by the fast and slow sets of lines of Experiment 3-B (bal- 

 anced selections after the direct selection of Experiment 3-A). The continuous 

 line is the curve of the fast set, the broken line is the curve of the slow set. The 

 ordinates are the averages, the abscissae the three-day periods. 



Fig. 14-d Curve of the difference (in favor of the fast lines) between the aver- 

 age number of generations per line per three-day period produced by the fast 

 and slow sets of lines of Experiment 3-B (balanced selection after the direct 

 selection of Experiment 3-A). The ordinates are the differences between the 

 averages; the abscissae, the consecutive three-day periods. Note the practical 

 uniformity of the difference under balanced selection. 



December 4 and succeeding days conjugating pairs were ob- 

 tained, some from the fast lines, some from the slow ones. 

 Though many of the ex-conjugants died, eventually representa- 

 tives propagating normally were obtained from six of the fast 

 lines and four of the slow ones of Experiment 3-B. 



It will be recalled that these animals, before conjugation, had 

 been subjected to opposite selection for thirty days, then to 



