[Source and differentiation of vitelline cells during seasonal regeneration of vitelline glands by the planarianDendrocoelum lacteum].
In the PlanarianDendrocoelum lacteum, the genital system degenerates after the egg laying season. It regenerates itself during autumn. The vitelline glands are the last to appear. They are exclusively reconstituted by neoblasts which migrate towards the oviducts, join themselves into cords, multiply by amitoses, enlarge and differentiate into vitelline cells. This differentiation characterizes itself essentially by a steady decrease of the nucleocytoplasmic ratio, an increase of the nuclear DNA amount, the appearance and accumulation of orthodiphenol granules in the cytoplasm.