z. Evidence is presented to show that, in Amoeba proteus, the membrane potential (--72 mV) and the streaming velocity (40 microns/sec) are both affected by changes in the ionic composition of the medium. 2. The membrane potential and streaming velocity are inverse functions of log external potassium chloride concentration over a wide range. Distilled water decreases the streaming velocity, although the membrane potential is raised. 3. Single penetrations in different parts of the cell and direct measurements using two internal micro-electrodes provide evidence for an electrical potential gradient in the cytoplasm along the axis of movement which approaches I volt/cm. The tip of a pseudopod appears to be positive with respect to the rear of the cell and negative with respect to the external medium. 4. Electrical potentials, positive or negative, applied to the rear of the cell, can be used to redirect the streaming in a chosen direction. Streaming is away from a negative electrode and towards a positive one. 5. The relationships between the membrane potential, the internal potential gradient and the motive force for streaming are discussed. A new theory is put forward for the bioelectric control of amoeboid movement.
et al., I937).
Watanabe et al. (1937) showed that there is a potential difference between z6