PERIODIC REORGANIZATION IN PARAMAECIUM 451 



Chromatin has just separated from the achromatic threads but 

 still retains its niicronuclear structure. The next step in form- 

 ing the anlagen is the distribution of the threads and the arrang- 

 ing of the coarser chromatic granules underneath the membrane. 

 This step has been effected in the anterior anlage shown in the 

 same figure. Figure 18 gives a clear idea of the completed an- 

 lagen and the two micronuclei from which they arose. Here 

 the granules have become smaller and the plasmatic character 

 of the structure is more evident because its staining capacity 

 for eosin has increased. The micronuclei show the chromatin 

 surrounded by a plasmatic layer highly stained with eosin. In 

 figure 19. the next division, which is the first in the new rhyth- 

 mical period of the life history, is completed in one pair of micro- 

 nuclei and is in progress in the third micronucleus which is lying 

 just above the one chromatin body shown in the figure, though 

 many were present in the cell. All the chromatin bodies are 

 represented in an animal from Line VI (fig. 21, pi. 2). Nearly all 

 are more or less spherical and the dissolution of the chromatin 

 is evident. Two macronuclear anlagen, lying close together, and 

 stained a reddish-blue, show marked paucity of chromatin. The 

 two functioning micronuclei are lying at the opposite ends of the 

 cell, while a spindle, in which chromatin has passed to the two 

 poles, is also visible. This spindle represents the same forma- 

 tion as that figured by Maupas in a conjugating animal ('89, 

 pi. 13, fig. 27). Above one of the chromatin bodies is seen a 

 small chromatin granule which may be interpreted as a degen- 

 erating micronucleus. 



The disintegration of the chromatin bodies, which are now 

 often surrounded by a clear area, is also progressing in the ani- 

 mal represented in figure 20 (pi. 2). The macronuclear anlagen 

 have lost their round contour and appear more or less irregular 

 while the two micronuclei are ready for division. The micro- 

 nuclear divisions are far more advanced in the specimen shown 

 in figure 22 (pi. 2) and the two spindles present indicate an 

 ensuing cell division. One micronucleus is apparently degen- 

 erating. Large vacuoles are usually present in the cytoplasm 

 during this period. 



