||Yeast (Saccharomyces cerevisiae) was grown according to Hartwell (17) at 24°C or with the same medium but containing 20% glycerol. After several days, the yeast adapted to this condition but grew very slowly. Determinations of nuclear diameter by phase-contrast microscopy, of height by electron microscopy, and of pore frequency by freeze-etching were done on cells during the exponential growth phase (48 h after plating). For determination of nuclear size the short and long
axis of 50 live cells were measured and averaged separately.