1. Tetrahymzena gcleii E possesses phosphatases (nucleotidases) capable of hydrolyzing nucleic acid and its components at a very rapid rate. Eighty per cent of the phosphate in 0.0005 M adenylic acid is released in 22 hours when the population level is 20,000 cells/ml.2. The enzymes are confined to the cells and are not released into the surrounding medium.3. The cells release phosphate most rapidly at two pH levels, 5.3 and 9.2, being most active in the acid range.4. Enzyme activity as indicated by phosphate release is greatest in the lag phase of the growth cycle. During the logarithmic growth phase, the released phosphate is taken up by the cells at a uniform rate.