EFFECT OF CONJUGATION 321 



Thus the rate for the progeny of the non-conjugants was 

 greater every day except one; and the mean rate for the non- 

 conjugants was ahnost exactly 20 per cent greater than for the 

 progeny of the conjugants. 



It is clear therefore that the progeny of the non-conjugants 

 have a great advantage, both as to rate of reproduction and as 

 to mortality. 



Experiment lie. The two sets in the watch glasses (fig. 2, 

 H and K) were allowed to multiply till June 22, then 10 individ- 

 uals were removed from each, isolated on slides, and their rates 

 of fission followed individually and compared. All multiplied 

 vigorously, in two days 8 of the conjugant progeny had divided 

 five times; 1 three times, 1 six times. Of the non-conjugant 

 progeny, 5 had divided six times, 2 five times, 2 three times, 

 while 1 died. Thus the two are now nearly equally vigorous, 

 the rate of fission being still a trifle higher for the non-conjugants. 



Experiment lid. The non-conjugants dealt with thus far 

 (Experiments 11, a to c) had come originally from the same 

 watch glass as did the conjugants (that is, from branch E, fig. 2). 

 But there was under propagation at the same time, another set 

 of non-conjugants (branch Z>, fig. 2), cultivated on slides since 

 March 4, while those just described {F to K, fig. 2) had been cul- 

 tivated in watch glasses (hence with more fluid) since May 15. 

 On June 7 a watch glass culture of this slide series {D, fig. 2) was 

 made, and left uniform with a watch glass culture (branch K, 

 fig. 2) derived from the conjugants of June 3. On June 22, 10 

 individuals were taken from each of these two watch glasses 

 (D and K, fig. 2), and cultivated on slides, in order to compare 

 their fission rates and general vigor. The results were strikingly 

 difl'erent from those thus far obtained; on account of their great 

 interest I give them in detail. 



Table 18 shows that, contrary to all our previous results, the 

 progeny of the conjugants A' are much more vigorous than those 

 of the non-conjugants D. 



Now, in the experiment which just preceded this (11 c), we saw 

 that in a test made on the same date as the present one, and with 

 conditions identical, the non-conjugants {H) with the same history 



