appear to be differences between species. However, there are rarely fewer than 12 or more than 30 in each sporocyst. The largest embryos of the germinal masses are at the ends and the production of free embryos in both mother and daughter sporocysts appears to be accomplished only by their breaking off. They are replaced by the growth of other embryos which in their turn separate from the masses; new embryos appear to be constantly formed from the germinal cells which persist in the germinal masses and multiply throughout the reproductive life of the germinal sacs. This mechanism for the multiplication of germinal cells in the strigeoid group produces in the mother sporocyst a sufficient number of daughters to fill completely the digestive gland of the snail host, and in the daughters the enormous numbers of cercariae which escape during the life of an infection. Up to the pres