PERIODIC REORGANIZATION IN PARAMAECIUM 469 



there is an inherent tendency for sister lines to undergo the 

 process synchronously. The significance of this will be consid- 

 ered later. 



The death of Line VI during the process indicates a fact which 

 we have noted several times in these experiments and one to be 

 expected when the complexity of the reorganization process is 

 appreciated. The animals at this time are in a relatively sus- 

 ceptible condition and consequently more readily succumb to 

 slight environmental changes. It is undoubtedly at such periods 

 that many cultures not bred under the most favorable conditions 

 have become exterminated, and the attending cytological con- 

 ditions have naturally been interpreted as the results of de- 

 generation. 



The cells during the process seem to be more opaque than 

 usual, their breadth is relatively greater, their total volume is 

 somewhat increased and their movements are considerably more 

 sluggish. Cells with this appearance defer division for. "about 

 thirty-six hours and are at the climax of the process. The ani- 

 mals at this time are more difficult to handle with a pipet owing 

 to the fact that they have a tendency to adhere to the glass or 

 to minute particles of debris, thus indicating the so-called misci- 

 ble state noted by Calkins, Erdmann, Popoff and others in con- 

 jugating forms. Also, animals in this condition will sometimes 

 burst on transference to fresh culture fluid medium or to a fixing 

 fluid' 



Thus, by the continued daily study of the animals and their 

 rate of division one finally becomes able to tell, with a consider- 

 able degree of accuracy, the occurrence of the process merely 

 by the use of a low power of a Zeiss binocular microscope. 



B. SERIES OF CELLS FROM LINES I, II, III, IV, V 



Line III, which was not under such close observation as line 

 VI, had the process at the 4065th, 4189th, 4237th, 4315th gen- 

 erations. Text figure 17 gives the graph of the division rate 

 averaged for five-day periods. One lowering of the division rate 

 occurred at generations 4140 to 4144. During this time the 



