THE RELATION BETWEEN HYDROGEN-ION CONCENTRATION AND VOLUME, GEL/SOL RATIO AND ACTION OF THE CONTRACTILE VACUOLE IN AMOEBA PROTEUS

¹ The Zoölogical Laboratory, Johns Hopkins University, and the Marine Biological Laboratory, Woods Hole, Mass.

1. As the hydrogen-ion concentration decreases from pH 5.5 the volume of Amoeba proteus in solutions containing sodium as the only metallic ion increases to a maximum at pH 6.0, then decreases to a minimum at pH 7.0, and then increases to a second maximum at pH 7.5; and the gel/sol ratio increases to a maximum at pH 6.5, then decreases very extensively to a minimum at pH 7.0, and then increases equally extensively to a second maximum at pH 7.5.

2. In solutions containing potassium as the only metallic ion the volume and the gel/sol ratio decrease to a minimum at pH 6.0 and then increase.

3. In solutions containing calcium as the only metallic ion the volume remains nearly constant, but the gel/sol ratio increases very rapidly and extensively and then gradually decreases; but the extent of change in this ratio varies directly with the hydrogen-ion concentration.

4. The rate of elimination of fluid by the contractile vacuole is practically independent of the hydrogen-ion concentration except in the region of neutrality where it decreases markedly. In hypertonic solutions it gradually decreases to zero.

5. The change in the rate of elimination of fluid by the vacuole in relation to hydrogen-ion concentration is so low in comparison with the change in rate of passage of fluid directly through the surface that it is negligible. The changes observed in the volume of the amoebae in relation to the hydrogen-ion concentration were therefore almost entirely due to changes in the rate of transfer of fluid directly through the surface, i.e. to changes in the permeability of the surface to water.