The ultrastructure of the follicle wall of the domestic fowl during the phase of rapid growth.

The development of a standard technique for fixing the developing follicle for ultrastructural studies is described. 2. The follicle wall is shown to be a multi-layered structure which exhibits a number of morphological changes concomitant with yolk protein transfer, the most significant of which are the intercellular channels which form between the granulosa cells during the fast phase of protein transfer.