Macronuclear Reorganization Process in a Vegetative Cell Cycle of Euplotes eurystomus

1. In view of the structural changes of the chromatin elements and nucleoli, some inquiries have been made into the process of nuclear-reorganization-the emergence and translocation of the reorganization band found in the macronucleus of Euplotes eurystomus. 2. The interdivisional stage is divided, on the basis of the structural features of the chromatin elements, into six phases of the resting, preparation, solution, reconstruction, duplication and post-duplication. 3. In the course of making these successive phases, chromatin granules are transformed into threads, duplicated, and then re-transformed into granules. 4. The reorganization band is not yet distinctly established when it emerges. In the stage of its translocation, however, the anterior half is differentiated into the solution plane and the posterior half into the reconstruction plane. 5. However, some variant forms are observed in its early stage. The earliest condition of the band differentiation is clearly demonstrated by the immature type, in which all the chromatin granules in the resting phase gradually transform themselves into the post-duplication phase without losing their heterogeneity. 6. An analysis of the phase transformation in various types of the reorganization process leads us to the conclusion that the reorganization band makes the portion in which all of the chromosomes become thready only to bring forth their duplication. 7. Further inquiries were made into the common occurrence of chromosome aggregates in the macronucleus. 8. The nucleoli grow in size in the preparation phase, which, however, disappear with the approaching of the band. But a few of the smaller ones still remain visible, proceeding to grow in the post-duplication phase