Advancing the onset of mitosis by cell free preparations of Physarum polycephalum

Mitotic divisions in the plasmodia of Physarum polycephalum were advanced by about 1 h by applying to the plasmodial surface extracts of other plasmodia. Advancement of mitosis was greatest when the extracts were prepared from plasmodia harvested at late G2. The activity in the extracts responsible for the advancement of mitosis was found to be heat labile and non-dialysable. It is suggested that this activity belongs to proteins responsible for the regulation of mitosis.