The Development and Structure of the Vitelline Membrane and Their Relationship to Yolk Mottling

PREVIOUS reports on the vitelline membrane have been conflicting with respect to its chemical composition, physical structure and average thickness. Liebermann (1888) reported that the vitelline membrane consisted of keratinous material. Lacaillon (1910) found three layers, the middle layer being cellular in structure, whereas the external layers were fibrous. Moran and Hale (1936) also reported three layers and concluded that the two external layers consisted of mucin while the middle layer was keratinous. McNally (1943) found that the vitelline membrane of the freshly ovulated yolk was formed from the collagenous membrane which lines the inner surface of the follicular epithelium. He reported that this membrane became swollen and was covered with a a layer of mucin during its passage down the oviduct. Reports on the average thickness of the vitelline membrane range from 15 microns (Lacaillon, 1910) to 47.74 microns (McNally, 1943). The mechanisms involved in the development of yolk …