The cuticle is smooth. The lateral alae extend from the middle of the oesophagus to the region of the spicules in the males, but in females they are extended further posterior to the middle of the tail or more. The anterior short "pharynx", the procorpus, is poorly differentiated from the remaining cylindrical portion of the oesophagus. Three sclerotized structures are present at the anterior end of the oesophagus. The posterior flaps of the valves of the bulb extend slightly into the dilated lumen of the intestine. The intestine at its commencement is broader than the bulb, and gradually narrows down towards the anus. The excretory pore is situated anterior to the usual pre-bulbar position, and is located at the beginning of the posterior third of the cylindrical oesophagus. It is surrounded by a crown of chitinous rod-like structures. The tail is sharply pointed in both sexes.

Since the careful pioneer work of Zeller (1872, 1876), Polystoma integerrimutn has drawn the attention of a number of workers, and this species is probably the best known of the Monogenetic trematodes. However, certain important inconsistencies have arisen in the literature on Polystoma integerrimum and related forms, particularly in the description of the genital system; in view of this a reinvestigation of the anatomy of this species was undertaken.