Cort, Ameel and Olivier (1944) reported on the germinal development in the mother and daughter sporocysts of Schistosornatium douthitti. They showed that in the early stages of the mother sporocysts the wall grows much more rapidly than the germinal material, producing inflated sacs in which the germinal cells are distributed along the inner surface of the wall. Multiplication of germinal cells is very rapid; the number was estimated to be between 150 and 200 in mothers about 4 days old. In mother sporocysts about a week old the germinal cells begin to develop into daughter sporocyst embryos. Apparently all or almost all of the multiplication of germinal cells occurs before any of them form embryos. The daughter sporocyst embryos remain attached to the wall of the inflated, sausage-shaped mothers until they reach a considerable size and are distinctly elongate. Even in later stages in which many of the daughters are ready to escape they fill only a part of the body cavity of the mother sporocyst. The development of the daughter sporocysts is quite synchronous, although a few germinal cells lag in development and a few embryos are sometimes present in older mothers from which almost all of the daughters have escaped. This produces a situation in which most of the daughter sporocysts in an infection are about the same age. In the 1944 paper the authors also gave a detailed account of their observations on the germinal development in the daughter sporocysts of S. douth itti. Their figures and descriptions showed a very considerable multiplication of germinal cells before any of them started to develop into cercarial embryos. They also suggested that in the older daughter sporocysts there might be a brief phase of multiplication by the formation of germinal masses. During the summer of 1951 further studies were made on the germinal development in the sporocysts of S. douthitti. To obtain the early stages, laboratory raised juveniles of Stagnicola palustris elodes (Say) were exposed to miracidia that had hatched from the eggs from experimentally infected white mice. The miracidia were poured into an aquarium containing large numbers of the juveniles. A rather low incidence of infecton was obtained, and many of the positive snails contained only one mother sporocyst. The observations on living material were checked by the study of sections of the mother and daughter sporocysts at different stages of development. Material for sectioning was preserved in position in the snails tissue with Bouin’s fixative. The sections were cut 71" in thickness and stained with Heidenhain’s iron haematoxylin.