Maclean, Norman (University of Edinburgh, Edinburgh, Scotland). Electron microscopy of a fission yeast, Schizosaccharomyces pombe. J. Bacteriol. 88:1459-1466. 1964.-The structure of the fission yeast, Schizosaccharomyces pombe, was studied electron microscopically, with potassium permanganate and osmium tetroxide as fixatives. The cell was found to be bounded by a cell wall, 1,000 to 2,000 A thick, and a cell membrane. A layer of material was found between the cell membrane and the wall. The central nucleus, 2 to 3 mu in diameter, was bounded by a nuclear membrane, seen in some pictures to be double. Osmium tetroxide fixation revealed a granular body within the nucleus, identified as a nucleolus. Cytoplasmic structures included numerous vacuoles (probably normally containing lipid), a number of membranes and vesicles (which may represent a poorly organized mitochondrial system), and numerous granules (probably representing ribosomes).