Structure of the female genital glands of the oviduct in the opisthobranch mollusc, Runcina.

Runcina is a small hermaphroditic opisthobranch which possesses a monaulic reproductive system. In previous studies the male copulatory apparatus, the structure of the spermatophore and also the process of oogenesis have been described. The present paper gives an account of the ultrastructure of the female genital glands of the oviduct. In Runcina the oviduct comprises three primary regions, the albumen gland, the egg capsule gland and the mucous gland. Eggs enter the fertilization chamber and as they pass the opening of the albumen gland they become surrounded by albumen or perivitelline fluid. The eggs appear to become encapsulated as they traverse the egg-capsule gland and are eventually stuck together by mucus to form an egg mass. The epithelial lining of the three glands consists of alternating ciliated and secretory cells. The characteristics in secretory products of the glandular cells are described, and are discussed with reference to the way they contribute to egg vestment.