[Distribution and ultrastructure of glycogen in the oocyte ofMusca domestica]

Fully grown oocytes ofMusca domestica contain large amounts of glycogen distributed in a characteristic pattern. Three cytoplasmic layers can be distinguished: 1. The periplasm which is free of carbohydrates and merely contains some lipid and protein yolk. 2. A zone of large glycogen clods. 3. Adjacent to this the central ooplasm where numerous lipid droplets and protein yolk spheres are found beside medium size glycogen clods. The glycogen areas are not surrounded by membranes, in contrast to the other yolk inclusions. Some possible interpretations of this ooplasmic pattern, which is already established during oogenesis, are discussed.