Pulsation of the Contractile Vacuole of Para- Mecium as Affected by Temperature

In view of the recent investigations on the effect of temperature changes on biological processes (Crozier, 1924-25, a, b; Crozier and Federighi, 1924-25; Crozier and Sfier, 1924-25, a, b; Glaser, 1924-25) it became of interest to reexamine the relation between temperature and the rate of pulsation of the contractile vacuole of Paramecium. Kanitz (1907) found in four different species of Infusoria that as the temperature was raised, the rate of pulsation of their contractile vacuoles increased, agreeing with the work of earlier authors, and Khalnsky (1911) reported similar results with _Paramecium caudatum. Such an increase in rate is to be expected, since the function of the contractile vacuole is chiefly to expel the waste products of catabolism, arising from oxidative processes which are accelerated by increased temperatures. If the rate of pulsation is determined solely by the rate of these oxidative processes, then the thermal increments, or temperature characteristics, for pulsation might have the values typical of other oxidative processes (Crozier, 1924-25, b). If other factors are also involved the increments might be different. Observations have been made on Paramecium 6audatum in order to determine the thermal increments for vacuole pulsation, which should assist in identifying the underlying and determining chemical reactions. The animals were secured from wild cultures, and were grown in hay infusions of constant concentration. Besides the Paramecia, which were always predominant, the cultures contained also smaller ciliates, such as Colpidium and Euplotes, and a few small rotifers. When animals from such cultures were studied it was found that the pulsation rate varied greatly in different individuals at the same temperature, although the rates obtained from 581