GAMETOGENESIS AND EARLY DEVELOPMENT OF THE POLYCHAETE GLYCERA DIBRANCHIATA

¹ Department of Biology, Catholic University of America, Washington, D. C., and Chesapeake Biological Laboratory, Natural Resources Institute of the University of Maryland, Solomons, Maryland

1. Information on gametogenesis in the bloodworm has been obtained by histological examination of material collected at Solomons, Maryland, in 1960 and 1961. The paired gonads begin in segments 45-47 and continue to about segment 110. They arise ventro-laterally, as retroperitoneal outgrowths near the opening of each parapodial cavity into the general coelom. Young oocytes and spermatocytes, the latter grouped in small clusters, are released from the gonads and mature in the coelomic fluid. Ripe oocytes are colorless, discoidal and about 140 µ in diameter; sperm are of the primitive type.

2. Insemination is followed by germinal vesicle breakdown, elevation of the fertilization membrane and both polar divisions. Pelagic stages appear within 14-20 hours and in a few days develop into unspecialized, apparently planktotrophic larvae. The further developmental process, including the period of metamorphosis and settling, remains completely unknown.