PERIODIC REORGANIZATION IN PARAMAECIUM 437 



contains many small vacuoles some of which may be filled with 

 bacteria (figs. 1 and 3, pi. 1). 



As the low point of the division rate approaches, the granules 

 of the macronucleus become more and more coarse, its staining 

 capacity increases, its form becomes more kidney-shaped and its 

 shorter axis elongates. Still more obvious changes of the macro- 

 nucleus indicate the actual beginning of the regulation process. 



1 . The macronucleus 



At this stage projections appear at the end of the macro- 

 nucleus (figs. 4 and 5, pi. 1) which are either merely thin 

 membranes devoid of chromatin or filled with small granules. 

 Hertwig ('89, p. 7) describes them as follows: '^gleichzeitig 

 verliert die Oberflache ihr glattes Aussehen; Einkerbungen 

 erstrecken sich mehr oder minder tief in das Innere hinein und 

 zerlegen den Kern nicht selten in drei ungleich grosse Lappen 

 oder es werden an den Enden fingerformige Fortsatze deutlich 

 oder leisten-und riffartige Vorspriinge," According to this 

 author they are not evident during the latest stages of vegetative 

 cell division, or in the first changes incident to conjugation. 

 Though Hertwig could not observe these projections in the living 

 animal he did not believe them to be artifacts because he could 

 demonstrate them with every fixation fluid. We have naver 

 observed them in vegetative cell divisions but frequently have 

 noted their presence several generations before the definite onset 

 of the process. We have no data in regard to their relation to 

 conjugation. 



Figure 5 (pi. 1) gives a good idea of these projections. The 

 animal figured is from Line VI, 4094th generation, and is nine 

 generations before the beginning of the reorganization process 

 which started in the 4103d generation. These long finger-hke 

 projections are preceded by the appearance of smaller ones (fig. 

 4, pi. 1) which seem to indicate that plasmatic currents are 

 present in the macronucleus though the membrane at this stage 

 is still intact. 



