EFFECT OF CONJUGATION 375 



multiplied scarcely at all, and the mortality was high. Tt was 

 almost impossible to get conjugation among its members, since 

 a prerequisite to conjugation is a period of rapid multiplication. 

 The necessary conditions were fulfilled only for three pairs. 

 From these, six ex-conjugants were obtained. The six lines of 

 propagation derived from these were compared with ten lines from 

 individuals that did not conjugate (and did not attempt to do so). 



There was no general rejuvenescence due to conjugation. 

 Three of the six conjugant lines died out within a week, and a 

 fourth a little later; so that two-thirds of the conjugant lines were 

 dead. But two continued to multiply. But in the mean time 

 all of the ten non-conjugant lines died out. 



What has happened here? We can hardly speak of rejuve- 

 nescence where two-thirds of the ex-conjugants die out. The 

 survival of some of the conjugants may have been due to the 

 greater vigor that was a prerequisite to their conjugation, the 

 lack of which caused the others not to conjugate. Aside from 

 this we can only say that the results of conjugation were here the 

 same as usual; it induced variation in the reproductive power. 

 As always, some lines derived from the conjugants had a low 

 reproductive power and died at once. Two out of the six had 

 greater reproductive power; they therefore continued to multiply. 

 In the meantime, the uniform non-conjugants, retaining the 

 original depressed condition, all died out after a short time. 



This experiment therefore gives, in fact, the same result as all 

 the others, an increase of variation as a result of conjugation. 

 It differs from the others merely in the fact that in two of the six 

 eases the extremes of variation reached a higher level than that 

 which characterized the animals before conjugation. The same 

 result is reached in Experiment 15, where the conjugants at the 

 upper extreme of the range exceeded in their rate of reproduction 

 the uniform non-conjugants. But in this latter case there is no 

 temptation to speak of rejuvenescence, since the non-conjugants 

 still continue to multiply vigorously. 



Thus, under exceptional conditions the production of variation 

 by conjugation results in preserving some representatives of a 

 stock which would otherwise die out completely. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 1-1, NO. 3 



