CONJUGATION AND ENCYSTMENT 357 



Others, e.g. (1910, 5/24-6/2), (1911, 5/2-11), (1911, 6/28-7/7) 

 the opposite is true in others, e.g. (1911, 5/22-31), (1911, 

 6/18-27). 



Numerous other similar instances appear throughout the whole 

 table. I would call attention in particular to the results ob- 

 tained in 1912, 6/6-7/30. In this whole series there is very little 

 difference between the coefficients of variation in the ex-conju- 

 gants and the conjugants separated. In the first three periods 

 it is a trifle larger in the former, in the next three a trifle larger in 

 the latter, etc. Five lines were maintained in both groups 

 throughout and there w^ere very few deaths in either. This is, 

 consequently, a very good test case. Taken as a whole the table 

 shows conclusively that ex-conjugants in Didinium are certainly 

 not consistently more variable in respect to the rate of fission 

 than are the non-conjugants. 



The evidence presented in the three tables seems to show 

 clearly that conjugation in Didinium has no appreciable effect 

 on the rate of fission or on variation in the rate of fission, and 

 that if it has any effect on death-rate it is a retarding effect. In 

 these respects there is a marked divergence between our results 

 and those obtained by Jennings on Paramecium. It seems quite 

 remarkable that in two closely related organisms the effect of an 

 apparently fundamental process should differ so greatlj^ 



The results taken as a whole seem to show conclusively that 

 neither conjugation nor encystment are rejuvenating processes, 

 at any rate, not in the sense in w^hich Calkins has used the term: 

 namely, to indicate a nuclear reorganization in which accumulated 

 waste materials are eliminated. iVnd they are clearly not in 

 accord with the results obtained by Jennings in experiments on 

 Paramecium. They do not, however, overthrow his theory of 

 the functions of conjugation. 



Jennings assumes that the production of favorable characters 

 is due, in the process of conjugation, to the union of nuclear sub- 

 stances which differ in potency. If therefore, the nuclear po- 

 tency of the conjugants is the same, one would not, in accord 

 with Jennings' contention, expect any favorable effect. The 

 didinia used in the experiments described in the preceding pages 

 were very closely, related. It may, consequently, be maintained 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 23, .NO. 2 



