Observations on N. dumerilii reared to sexual maturity in the laboratory showed sperm-shedding and egg-shedding processes, almost identical with N. limbata. Presence of mature 9 or eggs induces sperm-shedding; presence of sperm induces oviposition. Eggs of the 2 species show close resemblance in form, distribution, number of oil drops, and pigmentation. During swarming period, N. dumerilii exhibits precisely the same breeding behavior as N. limbata. There is never any indication of copulation so characteristic of Platynereis megalops. Observations negate suggestion that N. dumerilii and P. megalops are identical.