1. The effect of HCl, NaOH, CO2, and NH3 on the volume of unfertilized Arbacia eggs was tested over a wide range of pH values.
2. No swelling occurred, except in HCl solutions, and there not until after injury or death had occurred.
3. Whereas the volume of erythrocytes and of proteins such as gelatin is known to be dependent on the pH of the solution, such a relation does not exist in the case of living and uninjured cells, at least of the type tested.