PERIODIC REORGANIZATION IN PARAMAECIUM 479 



r J 



X 5t X % X 



Text fig. 16 Graph of the rate of division of line VI, subculture IE, averaged 

 for five-day periods. The periods during which the reorganization process oc- 

 curred are indicated by an X. 



actually rhythms, i.e., not obviously due to changes in the envi- 

 ronment, and at the low point of each of these rhythms the process 

 was in progress. Table 1 shows that the process in Line VI was 

 in progress at the 4057th, 4104th, 4140th, 4183d, and 4231st 

 generation when the line died. These generations represent ap- 

 proximately the climax of the process. Thus it is clear that in 

 the line under consideration the process occurred at intervals 

 of about 40 to 50 generations or about every twenty-five to 

 thirty days, and that the low point between each of the first four 

 fluctuations was coincident with the nuclear reorganization. This 

 evidence from Line VI shows clearly a relationship between the 

 rhythms and the nuclear reorganization. 



Cumulative evidence which establishes a casual relationship 

 between rhythms and the process is afforded by a study of Line 

 III which was carried continuously for eight months. Animals 

 from Line III were not preserved every day at the time of iso- 

 lation (as was the case with Line VI) owing to the great amount 

 of labor involved, but at intervals of several days duration. That 

 is, no attempt was made to have a complete pedigreed series of 

 stages showing its daily cytological condition but merely a broad 



