This is a cross section through an entire freshwater snail, infected with rediae of Echinostoma. The diameter of the section is about 8 mm. In an uninfected snail this section would be filled with coils of the host's ovotestis, digestive gland and intestine. However, the large number of daughter rediae here, which were produced asexually by mother rediae, have eaten away most of the snail's tissue. All that remains are about four large, irregularly shaped structures with dark margins and amorphous centres (which are probably loops of snail intestine) and a few smaller oval structures (G) with purple margins and clear centres (which are possibly ducts of the host's ovotestis or digestive gland.) All the remaining structures are cross sections through parasite rediae. The rediae have a thin wall (four of the many rediae present are circled) and are filled with sections through cercariae. The acetabulum can be seen on many cercarial sections. There may be 2000 rediae or more in a single snail.