Post-fertilization functions of annulate lamellae in the periphery of the egg of Spirorbis borealis (Daudin) (Serpulidae=Annelida)

Summary Post-fertilization changes in the periphery of the egg of Spirorbis borealis are described. The nuclear envelope and cell membrane are formed by the coalescence of short strands of membrane perhaps produced by the Golgi complex. Annulate lamellae are abundant in the forming cells giving rise to endoplasmic reticulum and apparently contributing to genesis of mitochondria. This possibility is discussed.We are grateful to Professor E. W. Knight-Jones in whose department the work was carried out.