AbstractEggs of the marine clamSpisula solidissimawere examined by the technique of freeze‐substitution. Morphology of the cytoplasm was investigated as a function of cellular water content using osmotic means to control water concentration. In eggs frozen in less than double strength sea water, ice crystallization usually occurred throughout the cell. In eggs frozen in double to triple strength sea water, 10–75% of the eggs were devoid of ice crystals in the cytoplasm and in triple strength sea water, also in the nucleus. From these results and from a detailed analysis of cells in which both ice crystals and ice crystal‐free regions occurred it is concluded that cells or parts of cells may be frozen free of ice crystals if their free water content is reduced. Reduction in free water content may occur in several ways: deliberate dehydration by osmotic means; accidental dehydration by evaporation of water from cells prior to freezing; osmotic dehydration of one region by an adjacent one in which ice crystallization is in progress. In ice crystal‐free cells, all common cell inclusions could be rec