64 RHODA ERDMANN AND LORANUE L. WOODRUFF 



Here the macroniiclear surface loses its smooth appeai'ance while 

 clefts and wrinkles appear in the stained preparations thus 

 indicating that in the living cell the distribution of the chromatin 

 is not homogeneous in the macronucleus (figs. 4 and 7). 



The micro nucleus begins to swell shortly after emergence from 

 its depression in the macronucleus. Figure 5, shows the chro- 

 matin arranged at the equator of the micronucleus in a band of 

 granules while one pole is nearly devoid of chromatin. (Compare 

 Calkins and Cull '07, fig. 1). The swelhng continues until 

 the so-called sickle stage appears. Figure 8 shows a more elong- 

 ated micronucleus than the one shown in figure 5. The for- 

 mation of the 'sickle' is completed in an animal from the 202d 

 generation, Culture Y, Line III g (fig. 7). The paucity of the 

 chromatin in the portion of the micronucleus which protrudes 

 from under the macronucleus is remarkable; no distinct granules 

 or threads being recognizable as the chromatin is apparently 

 homogeneousl}' distributed throughout the dividing micronucleus 

 at this stage. The formation of chromatin bodies has begun 

 in the macronucleus. Maupas, Hertwig and Hamburger de- 

 scribed, in the different species of Paramaecium which they 

 investigated, the occurrence of the 'sickle' stage before the onset 

 of the reduction divisions preceding conjugation. The 'sickle' 

 stage changes in conjugation into the first reduction spindle as 

 described in detail by Calkins and Cull, '07, p. 383, in Paramae- 

 cium caudatum. In the reorganization process of Paramaecium 

 caudatum we secured an animal from the 184th generation with 

 the very characteristic dumb-bell form of the micronuclear divi- 

 sion spindle (fig. 6). The 'dumb-bell' micronuclear division 

 stage in the reorganization process resembles closelj'- the stage 

 which Calkins and Cull ('07, fig. 15) interpret as the telo- 

 phase of the second maturation division in conjugation. In the 

 reorganization process of Paramaecium caudatum there is a 

 slight difference in size of the arising micronuclei as is indicated 

 in the cell shown in figure 6. The amount of chromatin at the 

 two ends is apparently different. It is possible that the arising 

 micronucleus which is nearly devoid of chromatin is the one whose 

 products after the next division are doomed to degeneration. 



