Studies were made on living material, supplemented by sections, of the development of the germinal cells in the germinal sacs of Paragoninum kellicotti. In the youngest mother sporocysts there is some multiplication of germinal cells, and soon the most anterior of them begin to develop into embryos. At later stages, besides the redial embryos which fill the body cavity, a few germinal cells and small embryos are found attached at its posterior tip. Between 20 and 30 mother rediae are produced by each mother sporocyst. In the mother redial embryos at about the time that the cells of the digestive system become well defined there is a morula-like group of germinal cells in the primitive body cavity. Soon the most anterior of these germinal cells develop into embryos and the majority of them have become embryos by the time the young mother rediae escape. A few germinal cels persist in older mother rediae which appear to be soon exhausted. Each mother redia produces about 30 daughters. In the early stages of the daughter redial embryos the development of the germinal material is like that in the mothers. However, in later stages, instead of the germinal cells having only a limited period of multiplication, they are found in rather large persistent germinal masses which are still present in mature and old daughter rediae. This very great extension of the period of multiplication of the germinal cells provides for the production of large numbers of cercariae.