EFFECT OF CONJUGATION 367 



delian recombination is not the whole secret of the matter; it 

 does not, however, demonstrate this. 



In a previous paper ('11), I have shown that conjugation hke- 

 wise increases variability in size. In the account of Experiment 9, 

 of the present paper, some data are given indicating that the size 

 differentiations so produced are likewise inherited. But the 

 results there gi\^en are by no means conclusive, the matter 

 requires further stud}'. 



It seems best to reserve for a later paper on inheritance a com- 

 parative review of what is known as to the production of variation 

 by conjugation in other organisms, with the various theories that 

 have been held. 



CONJUGATION AND BIPARENTAL INHERITANCE 



In a paper to be published at once, by the present author and 

 K. S. Lashle}^ it will be shown that conjugation results in inherit- 

 ance from both the parents that enter into the pair. All details 

 are reserved for the paper referred to; the matter is mentioned 

 here merely to complete the outline as to effects of conjugation. 



CONJUGATION AND THE THEORY OF REJUVENESCENCE 



The chief positive results from the present investigation are: 

 (1) that conjugation increases variation, giving rise to heritable 

 differentiations; (2) that it results in biparental inheritance (to 

 be taken up in a separate paper) ; (3) that the fission rate is lower 

 after conjugation; (4) that the mortality is as a rule higher, and 

 abnormalities are more common, among the descendants of con- 

 jugants than among those of non-conjugants. 



Wliat is the relation of these results to the theory that conju- 

 gation produces rejuvenescence? 



A number of diverse things have been included under reju- 

 venescence, the theory meaning for some authors one combina- 

 tion of these, for others another combination. The main points 

 included appear to be the following : 



1. The structural changes — the replacement of the old macro- 

 nucleus by a new structure derived from the micronuclei — has 



