The Relationship between Oocyte and Follicle in the Hen's Ovary as Shown by Electron Microscopy.

I N the adult hen each oocyte is surrounded by a capsule of follicle cells and all the raw materials that enter the oocyte must pass through this capsule. It is not surprising, therefore, that the morphological relationships between the follicle and the oocyte are of a highly specialized nature. Several workers have studied them, mainly by light microscopy, but their findings have not been unanimous, largely because of difficulties in resolving fine details. For instance, although it has frequently been suggested that certain structures pass from the follicle cell into the oocyte, these structures have been interpreted by different authors as Golgi bodies, as mitochondria or as fat drops. Similarly, there have been several different theories about the relationship between the cell membrane of the oocyte, the zona radiata and the vitelline membrane. Other problems that have not been solved are that of whether the follicle cells actively synthesize any materials for secretion into the oocyte, and that of what happens to the oocyte cell membrane just before ovulation. The present study is an attempt to solve these problems by an electron microscopical investigation of the follicular-oocyte region throughout the entire course of oogenesis. Recently, two other groups of workers using electron microscopy have reported on certain aspects of the early stages of oogenesis (see Discussion).