Ultrastructural study on oogenesis in shrews (Neomys fodiens, Sorex araneus)

The ultrastructure of early follicular oocytes is described. Among the differentiating organelles marked development of endoplasmic reticulum, often in close contact with mitochondria, is especially conspicuous. In addition, the dilatation of mitochondria, the accumulation of dense granular material and the formation of multivesicular bodies are discussed.