We have reported the unusual life cycle of Proterometra dickermani in which miracidia hatch from eggs produced by cercariae while still within germinal sacs in the molluscan host. During the summers of 1966 and 1968 our studies included the intramolluscan stages of P. sagittaria. Hatching miracidia within the germinal sacs were seen on several occasions. Although P. sagittaria does not regularly omit a vertebrate host, as does P. dickermani, these observations indicate that it does occur.