SYNCHRONIZATION OF MITOSIS BY THE FUSION OF THE PLASMODIA OF PHYSARUM POLYCEPHALUM

Abstract

The plats modium of Physarum polycephalum is multinucleated and exhibits synchronous mitosis. To obtain information on whether the timing of mitosis is regulated by cytoplasmic or nuclear substances, plasmodia from one period of the mitotic cycle were permited to fuse with plasmodia from other periods of the mitotic cycle. The sizes of the plasmodia to be fused were also varied to combine various proportions of material from periods early or late in the mitotic cycle into the fused plasmodium. The results suggest that substances responsible for mitosis are formed in the cytoplasm and increase in amount during the mitotic cycle, reaching a maximum just prior to mitosis.