Abstract
.1. Infection withDiplostomulum phoxiniis very common among minnows in the Glasgow area of Scotland.2. The first intermediate host of the parasite in this area is shown to be the freshwater snailLymnaea peregra.3. Adult flukes were obtained experimentally in mice, ducklings and herring-gull chicks.4. Significant differences are shown to occur between adult flukes recovered from different host species.5. The implications of these findings in relation to the host specificity and the classification of the Strigeida are briefly discussed.