The ontogeny of the sex organs of P. himalayensis, a member of the amphigynous group, was studied from the earliest stages of their formation up to the oospore stage. The view is held that the oogonial incept does actually penetrate the antheridi-um. Nuclear behavior during the various stages of copulation follows the same pattern as that in P. erythroseptica. The anthe-ridial nuclei are few, being generally 4, sometimes 7 or 8. The oogonial nuclei are variable and not more than 60 were observed. In both gametangia there occurs a degeneration of nuclei in which only 1 antheridial and 1 oogonial nucleus survive. These function in fertilization. Manocysts have not been seen in P. himalayensis. A unique type of gametangial copulation, in which antheridial papillae are involved, is descr. Owing to the origin of such papillae from amphigynous antheridia, and their homology with para-gynous antheridia, such a type of copulation demonstrates the fundamental similarity of amphigyny and paragyny.