The germinal cells of the rediae of Clinostomum marginatum are in groups of 2 to 5 free in the body cavity. In very small redial embryos only the germinal cell groups may be present. In older rediae they are mixed with the developing embryos. Only occasionally were single free germinal cells seen. It is postulated that these germinal cell groups must be dividing very rapidly to produce the large numbers of embryos that develop in the rediae of this species. It is suggested that they are the prototypes of the complex floating germinal masses of the strigeids.