The use of transmission electron microscopy to solve problems in the study of the female gonad in platyhelminths

The female gonad of the land planarians Geoplana burmesteiri and Microplana terrestris was investigated by means of electron microscopy and cytochemical tecniques. The female gonad of both the species shows the same basic anatomy and similar ultrastructural features. It consists of two small ovaries located ventrally in the anterior third of the body and of two lateral rows of vitelline follicles. Oocyte differentiation is mainly characterized by the development of the rough endoplasmic reticulum (RER) and Golgi complexes which appear to be involved in the production of egg inclusions of medium electron density which remain scattered in the ooplasm of mature oocytes. On the basis of cytochemical tests, demonstrating their protein/glycoprotein composition, these egg granules have been interpreted as yolk. In the vitelline follicles, vitellocytes show the typical features of secretory cells with well