Abstract
Using the Mongolian jird (Meriones unguiculatus) as a laboratory host for the cystic stage of the British horse strain of Echinococcus granulosus, the mode of development of brood capsules and protoscolices was studied histologically. The successive stages in development in secondary hydatid cysts are described and shown to correspond closely with previous observations on primary hydatid cysts. The usefulness of this experimental model for future ultrastructural studies is emphasized.