While studying the ultrastructure (Noury-Srairi 1988; Noury-Srairi et al. 1989) of the parasitic turbellarian Urastoma cyprinae, we found granules in the seminal vesicle, which are described herein. Specimens of Urastoma cyprinae (Graff, 1882) were collected from the gills of mussels, Mytilus galloprovincialis Lamarck, 18 19, from the Bassin de Thau (France, Mediterranean coast) and were fixed in glutaraldehyde with a sodium cacodylate buffer and post-fixed in osmium tetroxide. The seminal vesicle consists of an anterior part containing mature spermatozoa and a posterior part containing glandular granules (Fig. 1). Glandular granules are roughly spherical, with a diameter ranging from 0.5 to 1 pm (Figs. 2,3). Each granule contains a central core of amorphous electron-dense material and tubules arranged as one to three peripheral coils (Fig. 3). The tubules are about 40 nm in diameter and have a hollow center (Fig. 3). The glandular cell (Fig. 4) that produces the granules occurs in the parenchyma close to the seminal vesicle. The glandular granules show (a) a roughly spherical shape, (b) an amorphous electron-dense center, and (c) several peripheral coils of tubules. In the Platyhelminthes, only a single described structure is known that slightly resembles these