1. A special technique has been developed for transfer of sea urchin eggs (or other suitable objects) from one solution to another under anoxic conditions while under microscopical observation. The transfer is done with a fine glass loop in an anoxic micromanipulation chamber. 2. Unfertilized eggs of Arbacia punctulata were subjected in an atmosphere of pure hydrogen (and water vapor) to treatment with certain chemical and physical agents which in air are known to produce a cortical response, followed usually by membrane elevation. 3. A typical cortical response, usually followed by membrane elevation, was obtained in complete absence of oxygen by treatment with ¼ per cent saponin in sea water, isotonic urea solution, or isotonic sucrose solution, or by micro-puncture. The time relations were the same without oxygen as with it. 4. Transfer of unfertilized Arbacia eggs in urea solution, followed by several washes of sea water, all under anoxic conditions, led to cleavage after readmission of air. Thus the treatment which initiates cleavage does not require oxygen. 5. The amoeboid movement of unfertilized Arbacia eggs in isotonic urea solution was stopped reversibly in absence of oxygen. Cleavage also is known to require oxygen; but it was found that amoeboid movement took place at an oxygen tension well below that required for cleavage. 6. Unfertilized Arbacia eggs in urea solution immediately stopped all movement when the hydrostatic pressure was raised to 340 atmospheres. If the pressure was raised to 230 atmospheres or more before the eggs had begun to lose their spherical shape, no movement occurred. This inhibition of movement was reversed when the pressure was released. 7. Unfertilized eggs which had been compressed to 680 atmospheres for several minutes showed no ill effects, and when inseminated afterwards at atmospheric pressure gave good fertilization membranes.