Abstract
1. The distribution of acid and alkaline phosphatases in the hepatopancreatic cells of the molluscan host of Echinoparyphium sp. and in the redia and cercaria of this trematode has been studied.2. There is a heavier concentration of acid phosphatase in the hepatopancreas of infected snails than in uninfected snails.3. No acid phosphatase is present in the bodies of the rediae or cercariae but this enzyme is present in the contents of the redial caeca.4. Alkaline phosphatase activity is greater in the hepatopancreas of infected snails than in uninfected snails.5. Alkaline phosphatase is present in the tissues of the rediae and the cercariae, especially in the fully developed cercariae.6. It is suspected that the increase in acid and alkaline phosphatases in Helisoma trivolvis infected with Echinoparyphium redia is correlated with the breakdown of glycogen by the parasite.This research was made possible by Grants E-3443, E-3443C1, and AI 3443–03 from the Institute of Allergy and Infectious Diseases, National Institutes of Health, U.S. Public Health Service. The author is grateful to Mr Randall W. Snyder, Jr., School of Medicine, The University of Virginia, for technical assistance.