R. T. YOUNG. 



With the second of these conclusions I am wholly in accord, 1 

 agreeing as it does with the results of my own work (/. c.}. The 

 first is not however in accord with my experiments and cannot I 

 believe be verified by a critical reading of Woodruff's own results. 

 That the periodicity of the rhythms is subject to greater vari- 

 ation than he admits may be deduced from his own data. In 

 order to show this Ihave compiled a table based upon the graphs 

 and tables of several of his own and Miss Erdmann's recent 

 papers, the exact source of the data being indicated in every case. 



In this table are shown the number of five-day periods, gener- 

 ations and variation percentages of the rhythms in various lines 

 of Paramecium aurelia, based on data the source of which is indi- 



1 Using "rhythm" as synonymous with inter-endomictic period. 



2 According to Woodruff's data there is a little uncertainty regarding the occur- 

 rence of endomixis at generation 4140 in line III. I have based my data on the 

 assumption of its occurrence at that time which he states was "almost positive" 

 (/. c., p. 470). 



3 Uncertainty exists in Woodruff's data regarding the occurrence of endomixis 

 at period 14. My table is based on the assumption of its occurrence there, which 

 he considers very probable judging by "the character of the curve" (/. c., p. 56). 



