[Ultrastructure of the follicular epithelium in the ovary of the domestic duck during the period of slow growth of the oocyte].

The work describes ultrastructural changes in the follicular epithelium and ooplasm in the period of the slow oocyte growth. The morphology of follicular cells (well-developed endoplasmic reticulum, numerous free ribosomes) is considered as evidence of their synaptic activity whereas the morphology of ooplasm indicates to its accumulative function. It is supposed that at this stage nutritive substances enter the oocyte through the intercellular spaces and their absorption is brought about by means of microvilli on the oocyte surface. A specific organelle of the avian egg -- so called transosome, is described. Their structure, transposition and possible function are discussed.