Gametogenesis in Vaucheria

Abstract

Spermatogenesis was observed in V. sessilis, V. pachyderma, V. aversa, and V. geminata. The discharge of the sperms (usually between 1 and 3 a. m.) was observed in the first 3 spp. but not in V. geminata. In the first 3 there is a large, distinct, peripheral layer of protoplasm (the "Wander-plasm" of Oltmanns and Heidinger) which migrates from the oogonium back into the main thread. In V. sessilis the "Wanderplasm" initiates the formation of the oogonium. In V. aversa stained material showed that practically all of the supernumerary nuclei, sometimes as many as 400, migrate back into the main thread with the "Wanderplasm." In V. geminata the "Wanderplasm" passes back out of the oogonium, carrying most of the supernumerary nuclei; some, however, appear to remain in the oogonium to degenerate. In V. sessilis, V. pachyderma, and V. aversa the basal wall of the oogonium is formed 1/4-1 hr. after the "Wanderplasm" has passed out, and from a few minutes to 1 hr. before the oogonium opens.