The role of the follicle cells during oogenesis in the chiton Sypharochiton septentriones (Ashby) (Polyplacaphora,Mollusca)

Summary Histochemical studies and electron microscopic investigations on the role of the follicle cells during oogenesis in the chiton Sypharochiton septentriones showed that the main role of the follicle cells was the deposition of a spiny chorion around each oocyte. The chorion was composed of three layers; an inner, acid mucopolysaccharide layer, which was a primary egg membrane secreted by Golgi bodies in the cortical cytoplasm of the oocyte, an intermediate layer of protein and an outer layer of lipid. The intermediate and outer layers were secreted by the follicle cells and were thus secondary egg membranes.