300 H. S. JENNINGS 



Summary of results. Experiment 2 gives the following general 

 results : 



In three sets of individuals taken from the same culture and 

 treated in the same way, one set that was allowed to complete 

 conjugation, another separated before union was complete, and 

 a third that had not yet begun conjugation: 



1. Those that had completed multiplied throughout less 

 rapidly than those that did not complete conjugation, and less 

 rapidly than those that had not begun conjugation. This dif- 

 ference persisted throughout the experiment; that is, for eight 

 weeks after conjugation had occurred. 



2. The descendants of those that had completed conjugation 

 were much more variable in their rate of fission than those that 

 did not conjugate. 



3. The mortality was slightly greater among those that had 

 completed conjugation than among the others. 



4. There was no marked difference in these respects between 

 the set that were separated after beginning conjugation, and the 

 set that had not yet begun. 



Experiinent 3: June 20 to June 24, 1909: Effect of high 

 temperatures 



This experiment lasted but four days, and was designed 

 primarily to test the relative variability in the dimensions ot 

 the progeny of conjugants and of non-conjugants. The results 

 on this point have been given in my paper of 1911, on Assortative 

 mating, et cetera (table 32, p. 99). Here will be given the results 

 of the experiment so far as they bear upon the comparative vitality 

 and the rate of reproduction in conjugants and non-conjugants. 



In the experiments which we have thus far described, the 

 conjugants reproduced more slowly than the non-conjugants, 

 while at the same time the mortality of the conjugants- was 

 higher. It appears possible that under some conditions the 

 greater rapidity of fission of the non-conjugants might be dis- 

 advantageous, causing greater mortality in them than in the 

 conjugants. This possibility is realized in the present experi- 



