Nuclear behavior in the life cycle ofGanoderma lucidum(Leyss. ex Fr.) Karst., a common polypore in West Bengal, India, has been studied. Each young basidium is binucleate and the nuclei soon fuse to form a syncaryon which undergoes three successive divisions, of which the first is reductional, to produce eight daughter nuclei. Four nuclei pass into the four spores, one into each, and the other four, remaining within the basidium, finally degenerate. Thus at first each basidiospore contains one nucleus which may or may not divide further. On germination, the spores give rise to primary mycelia with uninucleate or multinucleate cells. Secondary mycelia, formed by the union of two compatible primary mycelia, have nodose-septate hyphae in which most of the cells are dikaryotic although cells with more than two nuclei are not uncommon.The chromosome number, counted from metaphasic plates, has been found to be 10 = 2n.