1919] Rhodes: Binary Fission in Collodidyon triciliatum Carter 231 



macrokaryosome at the time of the splitting of the peripheral granules, 

 or when it persists and is found on or near the equatorial plate 

 (pi. 11, fig. 46). As noted above, it may (pi. 12, fig. 48) pass un- 

 divided to one of the poles and thus to one of the daughter nuclei 

 (pi. 12, fig. 56). This would explain the inequality of the anaphase 

 ehromatin masses. It may disintegrate (pi. 11, fig. 43), go into solu- 

 tion, and finally enter into the composition of the chromosomes. It 

 may, which is very probable, pass from its niche in the nuclear mem- 

 brane, out of the nucleus to form an extranuclear chromidial cloud 

 or simply be dissipated or absorbed into the cytoplasm. It was found 

 to divide into two unequal segments in several instances in the early 

 prophase (pi. 10, fig. 33), but it is hardly probable that much signifi- 

 cance attaches to this, since it is not coordinated with ehromatin 

 divisions elsewhere. 



ANAPHASE AND TELOPHASE 



After the transverse splitting and separation of the chromosomes, 

 each daughter group passes toward its respective pole. When only 

 slightly separated, the chromosomes fuse into a densely staining 

 mass (pi. 12, figs. 52, 54, 55), but can hardly be said to lose their 

 identity here, since knobs and masses resembling ends of chromo- 

 somes protrude irregularly from the mass. These ehromatin masses 

 become organized into a skein or spireme, a great number of small 

 granules arranged on linear linin threads, before the nuclear mem- 

 brane has divided (pi. 12, fig. 53). The spindle fibers still persist 

 (pi. 12, fig. 52) after the daughter ehromatin masses have drawn near 

 their respective poles, but are only slightly visible at the former 

 equatorial plate. The nuclear wall constricts and nuclear division is 

 accomplished, with the ehromatin still in compact masses. 



As the daughter ehromatin masses pass to their respective poles, 

 they increase perceptibly in size until each equals or exceeds the size 

 of the original karyosome (pi. 12, figs. 52, 55). This is evidently 

 growth and not concretion or deposition, since the chromidial cloud 

 practically disappears at the metaphase and then deepens again in 

 the anaphase. 



Toward the final anaphase the ehromatin mass or skein breaks up 

 into numerous ehromatin masses scattered irregularly through the 

 daughter nuclei. A cloud seems to fill the nucleus and spreads to 

 the surrounding cytoplasm, indicating excessive metabolic activity. 



