Experiments were designed to determine the rate of gain of heat-tolerance for three different groups of goldfish, Carassius auratus, respectively acclimated to 4°C., 12°C., and 20°C., and subsequently moved to a temperature S°C. higher. The rate of change of heat-tolerance showed a marked difference in the three greups, twenty or more days being required for complete acclimation in the 40C. gro...
