InHelcion pellucidusthe cytoplasm of spermatogonia contains granulo-fibrillar dense bodies, a Golgi apparatus and a pair of centrioles. In primary spermatocytes a flagellum arises and putative small dense proacrosomal vesicles are formed from golgian activity. The mature spermatozoon is of the primitive type and does not contain a perforatorium. Silver stained the centriolar fossa, the periphery of centrioles and the pericentriolar complex, while phosphotungstic acid-chromic acid did not stain the acrosome. Similar cytochemical results were obtained inPatella rustics. The different morphological aspects of spermatogenesis in Patellogastropoda and Archaeogastropoda and the use of silver and PTA stainings in the Mollusca are reviewed and discussed.