Feeding and digestion in two species of triclad Turbellaria, one aquatic, the other terrestrial, were investigated by histochemical methods to locate and identify a selection of the enzymes concerned in the two processes. In both species the pharynx possesses acidophil gland cells which produce endopeptidases of the cathepsin C type and the available evidence indicates that these are used to assist the pharynx in its penetration of the prey and subsequent disruption of the latter''s body contents prior to their ingestion. In the gut food is attacked by endopeptidases similar to those of the pharynx and originating from the sphere cells of the gastrodermis. This initial extracellular digestion is followed by phagocytosis of the semidigested food by columnar cells of the gastrodermis and completion of digestion intracellularly by endopeptidases, exopeptidases such as leucine amino-peptidase, a lipase and unidentified carbohydrases. Endopeptidase activity occurs at pH 5.0 and the remainder of the processes at pH 7.2. Acid phosphatase appears in the cells during endopeptidase activity and is eventually replaced by intense alkaline phosphatase activity during subsequent stages.