SUMMARYDipodascus uninucleatuswas obtained in culture from a dead pupa ofDrosophila melanogaster.The vegetative growth is yeastlike and no asexual reproduction occurs. The fungus is homothallic. The cells are consistently uninucleate. The asci arise from the fusion of two undifferentiated uninucleate cells and develop after nuclear fusion. The mature asci are elongate, multispored and bear a marked resemblance to those described forDipodascus albidusLag.D.uninucleatuspossesses characters which suggest a closer relationship of the genus Dipodascus with the Endomycetaceae than has hitherto been recognized.