Vegetative nuclear division was studied in Penicillium notatum and P. chrysogenum using light microscopy of stained preparations. The results obtained revealed mitoses in which duplicate sets of chromosomes were equitably divided into daughter genomes by successive division stages. From the resting stage consisting of a shell of granular chromatin, the dividing nucleus entered into a more densely staining stage containing chromosomes which appeared to be arranged in the formation of coiled cords. In the next stage of division the chromosomes became oriented into two parallel units and were then aligned in two's in a rectangular configuration. Division proceeded by movement of chromosomes to opposite poles. Mitosis included the development of a thin fiber which began as a deeply staining granule at one side of a spherical nucleolus. The granule divided into two components and then the thin fiber elongated between them.