While some workers have studied cytochemical localizations during oogenesis in molluscs (e.g. Arvy, 1949, 1950; Bretschneider & Raven, 1951; Collier, 1960; Cowden, 1961; Pasteels & de Harven, 1963), others have examined the ultrastructure of the developing oocyte using the electron microscope (e.g. Rebhun, 1956a, b, 1961; Worley & Hershenov, 1960; Pasteels & de Harven, 1963). This work has been...
