Motility of the oocyte of Helisoma (Mollusca).

Mature oocytes isolated from the ovotestis of Helisoma showed amoeboid movement when treated in vitro with a homogenate of the cerebral ganglia (containing dorsal bodies). This movement ceased when either cytochalasin B or colchicine was added to the preparation. Actin filaments were only visualized in in vitro and in vivo preparation of mature oocytes. We suggest tht in order to ovulate, the oocyte uses its own contractile system to become amoeboid and is thereby separated from the envelope of the follicle cells. We also suggest that the ovulation factor(s) is present in the dorsal bodies and that this factor could be responsible for the induction of microfilaments.