I. Cytoplasm. 1. The normal cytoplasmic pH, colorimetrically determined, of the starfish eggs in the unfertilized, fertilized, and first and second cleavage stages is 6.7 +/- 0.1. 2. Cytolysis lowers the pH to a value 5.5 +/- 0.1. 3. The cytolyzed material in time assumes the pH of its environing sea water. 4. The acid due to mechanical injury can also be detected in the environment of the egg. 5. Injury to the cytoplasm unaccompanied by visible disintegration causes an increase in acidity which is quickly neutralized. II. Germinal Vesicle. 6. The intranuclear pH, colorimetrically determined, of the immature Asterias egg is 7.5 +/- 0.1. 7. Injury to the nucleus does not change its pH. 8. The spherical nuclear remnant which persists after injury gradually assumes the pH of its environment. III. Plasmalemma. 9. A dye to which the cell is normally impermeable can penetrate through a tear in the surface from an environment more acid than normal. This may be due to a difference in the formation of the plasmalemma in a normal and an acid medium.