Electron-microscopic analysis of germinal material in mother sporocysts of Echinostoma caproni (Trematoda)

were performed. Germinal elements in miracidia are represented by undifferentiated cells and germinal cells. They are localised in the posterior half of the body and form the primordium of the germinal mass, which plays the role of the gonad. In mother sporocysts the germinal mass is located caudally and plays the dual role of the gonad and the uterus. In addition to the undifferentiated cells and germinal cells, it contains embryos, which develop there up to the stage of germinal balls and then move into the sporocyst's schizocoel, which plays the role of the brood chamber. New germinal cells are formed only by division of undifferentiated cells. No differences between undifferentiated and germinal cells in miracidia and those in sporocysts were found.