290 H. S. JENNINGS 



1 billion, 256 million progeny, while the 59 lines derived from those 

 that had not conjugated had a production of 48 billion, 467 mil- 

 lion, so that the non-conjugants produced somewhat more than 

 38 times as many progeny as the conjugants. The very great dif- 

 ference between the two in this respect arises from the fact that 

 many of the conjugant lines died out before the end of the experi- 

 ment and the further fact that the number of progeny increases in 

 geometrical ratio as the number of fissions increases in arithmeti- 

 cal ratio. To this latter fact is due also the seemingly excessive 

 differences in the number of progeny produced in the different 

 weeks, as shown in table 3. Unfavorable temperature or culture 

 medium, decreasing the number of fissions by a small number, 

 decreases the progeny enormously. 



To sum up on this point, the experiment shows clearly that 

 those that have not conjugated multiply more rapidly than those 

 that have conjugated, and the difference persists for at least four 

 weeks after conjugation. 



Variation. A careful examination of the data given in table 

 29 will show that there is more variation (among the different 

 lines) for the number of fissions in any given period, for those 

 that have conjugated than for those that have not. To deter- 

 mine accurately the differences in this respect, it is necessary to 

 determine the standard deviations and coefficients of variation for 

 each period. These are given in table 4 together with a compari- 

 son showing what the ratio of the variation among the non-con- 

 jugants is to that among the conjugants. 



Table 4 shows that in every week, and in every combination 

 of weeks, without exception, the variation is greater in those 

 that have conjugated than in those that have not. It is greater 

 in the conjugants, whether measured absolutely, by the standard 

 deviation; or relatively to the mean, by the coefficient of varia- 

 tion. In many of the periods the coefficient of variation is for 

 the non-conjugants but one-third to one-fourth of that for the 

 conjugants. 



It is then a simple statement of fact to say that in this case 

 conjugation increased greatly the variability in the fission rate. 

 Examination of table 29 shows that this great increase of varia- 



