Proceedings of the Helminthological Society of Washington

SUMMARY Studies were made of the germinal development in the mother and daughter sporocysts of C. elephantis in experimental infections *of the snail intermediate host. A few infections of another species with a much larger cercaria also developed in the experimentally infected snails . Very rapid multiplication of the germinal cells takes place in the early stages of the mother sporocysts and some of them have developed into embryos in three day old mothers only about 0.1 mm. long. The mother sporocysts grow rapidly in size and those about 1 min in length contain over 100 germinal elements most of which are embryos. By the time that mother sporocysts are 3 mm in length in 10 to 12 day old infections the number of germinal elements has increased to over 300, but the largest daughter sporocyst embryos are small "germ balls" only about 0.03 mm in diameter. After this, the embryos grow very rapidly and daughter sporocysts begin to migrate to the digestive gland of the snail about 21 days after infection . In embryo daughter sporocysts about 0 .1 mm in length the body cavity is well defined and the inner layer forms a large anterior plug . Such embryo daughters contain about 12 to 16 germinal cells and a few embryos. Daughters of C . elephantis at the time they escape from the mothers contain about 25 to 35 cercarial embryos and some germinal cells attached to the wall . The largest embryos at this stage are still very small but after the daughters have reached a size of from 1 to 2 mm they develop rapidly into cereariae, the first of which escape from the snail host about 5 to 6 weeks after infection . The pattern of germinal development in the germinal sacs of the spirorchiids is similar to that in the schistosomes . It is characterized by very rapid multiplication of the germinal cells in the early stages of development of both the mother and daughter sporocysts . No germinal masses are produced . The germinal cells become scattered along the wall of the body cavity and continue to divide and produce new embryos in the mother sporocysts long after the first daughters escape . In the daughter sporocysts new embryos are still being produced when the infections have become mature and the first cercariae have escaped .