1. Methods of collecting paramphistome eggs, largely freed of faeces, and their hatching are described.
2. Young B. tropicus were readily infested with paramphistomes: only 12.4 per cent of adult snails were infested.
3. Two methods of infestation are described.
4. The mass production, collection and counting of metacercariae are described.
5. After exposure to a 40 watt yellow electric light bulb at 1½ inches above the water surface 98.6 per cent of cercariae were shed within five hours.