The phosphatases in the cytoplasm and nuclei of Drosophila salivary glands are better preserved by fixation in absolute acetone than in 85 per cent, alcohol. In whole glands there is relatively little extraction of the enzyme during assay. Phosphatase activity is more resistant to incubation at neutrality than at pH 8.6, but in this material there is sufficient residual enzymatic activity to permit redetermination of alkaline, neutral, or acid phosphatase activity by staining methods after an initial quantitative determination. The state of the membranes of the gland affects the penetration of the substrate sufficiently to limit the activities obtained.

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