EFFECT OF CONJUGATION 



333 



not conjugated. Of the conjugants 20 died during the first week; 

 of the non-conjugants 18, leaving 58 and 82 respectively in the 

 two groups. 



Rate of fission. The ex-conjugants, as usual, began divid- 

 ing the second day after conjugation. Beginning for both sets 

 at this time, daily records were kept of the number of fissions in 

 each line. Table 20 gives the fissions for the first week, in each 

 of the two sets. As in all our other experiments, the rate of 

 fission was somewhat greater in those that have not conjugated. 



TABLE 20 



Experiment 13 a. Paramecium aurelia. Comparative number of fissions in con- 

 jugants and non-conjugants of the sarne culture, for a period of one week, begin- 

 ning two days after the separation of the pairs. 



Variation. As in other cases, the variation in the rate of 

 fission is much greater among the descendants of the conjugants 

 than among those of the non-conjugants. The standard devia- 

 tion is twice as great, and the coefficient of variation two-and-a- 

 half times as great, in the descendants of the conjugants (table 20). 



Mortality. Of the 78 conjugant lines, 20 died out during the 

 first week, or 25.6 per cent. Of the 100 non-conjugant fines, 

 18 died out, a mortality of 18 per cent. 



Experiment 13 h: inherited differentiations in the pure strain. 

 At the end of this first week, those lines of each set that showed 

 indications of differentiation in rate of fission were selected for 

 farther propagation. That is, from both the conjugant set and 

 the non-conjugant set the extreme lines were taken; also certain 

 of the intermediate ones. Thus, from the conjugant lines there 

 were selected the four that had not divided at all (table 20), the 



