IN the ascus of Neurospora, meiosis and mitosis appear to resemble those in higher plants1–4. However, within the mycelium of Neurospora and of a number of other fungi, some observers report that the conventional stages of nuclear division are lacking, that the spindle is absent, and that the nuclei divide by becoming constricted and pulling in two5–8. We too have found that mitosis in Neurospora mycelium is unlike that in higher plants and animals and that there is no spindle ; but we have observed also that the nuclei are filamentous (Figs. 1–4) and that they divide by splitting longitudinally.