, pl. rediae Intramolluscan development stage of a digenetic trematode, following the primary sporocyst stage, which forms after penetration of the snail tissues by the miracidium. Rediae are produced from cells within the sporocyst, are liberated from the latter, and develop in the tissues of the host snail as elongated, saclike, muscular organisms with a mouth and gut. The rediae may produce one or a number of additional generations in the snail, but they ultimately produce the final development stage, the cercaria.sporocyst (1), miracidium. [F. Redi, Italian physician, 1626-1697]