1. The passage of deuterium oxide across the egg membranes of Acheta commodus has been studied.
2. Deuterium oxide enters the egg at times when its weight is constant and leaves the egg at times when its weight is increasing as a result of uptake of water.
3. It is considered unlikely that these findings can be accounted for by simple exchange with hydrogen atoms in the membrance.
4. It is concluded that the shell membrances are permeable to water at all times.
Previously called Gryllulus commodus (Browning, 1952, 1953).