CYCLES OF REDUPLICATION IN MEGAKARYOCYTE NUCLEI

1. Estimates of the number of dividing megakaryocytes with mitotic apparatus have been obtained in intact and in phenylhydrazine-papain treated rats. 2. In treated rats chromosome morphology was studied using colchicine and hypotonic treatment. 3. In bone marrow smears and in cultures two systems for nuclear reduplication were demonstrated: C-mitosis, and multipolar mitosis without cytokinesis. 4. In phenylhydrazine-papain treated rats, the mitotic index of each bone marrow cell series was greatly increased.