446 



LORANDE LOSS WOODRUFF. 



period of over 100 days before it died, though the character- 

 istic 'rhythms' in the division rate are apparent during this 

 time. It is possible that the process did occur at about periods 

 19 and 25 (cf. Fig. 2) and was overlooked, but I believe that this 

 is highly improbable in view of the thoroughness of the search. 



Subculture Ot underwent endomixis at periods 4 and 9 and 

 then died without repeating endomixis at the next expected 

 period (cf. Fig. 2). 



Subculture Bt, as the graph shows, had endomixis at the 28th 

 period, just before the experiment was concluded. From the 

 character of the curve it would be expected at period 23, but it 

 was not observed. 



The endomictic periods of the four subcultures (3 races) of 

 Paramecium in this experiment may be tabulated as follows : 



These experiments show three points of considerable interest. 

 In the first place they corroborate, for races bred under con- 

 stant culture conditions, what was found in the same races 

 when bred under varied culture conditions in the experiment 

 already described. That is, At, AEt and Ot show a perfect 

 synchronism of endomixis, and this is most reasonably explained 

 by assuming that the general culture conditions, at least initially, 

 influenced the appearance of endomixis and that, once established, 

 the rhythmic period characteristic of the organism persisted. 

 Bt affords no data for comparison with the other races of this 

 set of cultures, as they had ceased to show endomixis before Bt 

 was started. 



A second point of importance is that the 'rhythms' in the 

 division rate are to a certain extent independent of endomixis 

 that is of the definitive series of nuclear phenomena because 

 the rhythms persist for a while in the absence of the morpho- 

 logical changes. One may suggest that the rhythms in the 

 culture are an expression of the physiological conditions ante- 

 cedent to the definitive onset of the nuclear changes in other 



