Rate of gain of heat-tolerance in goldfish (Carassius auratus).

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. group, seven days for the 12°C. group, and just over three days for the 200e. group. These results have been compared with those of Doudoroff (1942) and other investigators on rates of acclimation in fishes and an interpretation made of the natural changes in temperature acclimation of the bullhead, A meiurus nebtdosus, in lake Opeongo from May to September, 1941.