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The submicroscopic structures of protoplasm may be assumed to exist in part as aggregates, some of which are visible with the microscope. Entering into the formation of these aggregates is a great variety of substances, i.e., proteins, lipids, glucosides, and inorganic ions. Basic to the nature of protoplasm appears to be its ability to undergo reversible sol-gel transformations, These may be observed by noting variations in protoplasmic flow in the slime mold Physarurn polycephalurn.Haas ('53) injected a variety of enzymes into this slinie mold and has observed directly changes in protoplasmic streaming. For example, he found that certain proteinases, collagenase, some polysaccharases, and ribonuclease produce characteristic changes in protoplasmic activity, which reflect the action of these enzymes on the submicroscopic structure of protoplasm. He interpreted solation and gelation as a response to enzymatic activity which causes a loosening and reestablishment of specific bondings. Heilbrunn ( '52) especially has emphasized the role of calcium in causing gelation and solation of protoplasm. However, it is not clear how changes in the amount of free or protein-bound calcium may be controlled in vivo. The work reported here is an attempt to relate some possible enzymatic activities to changes in the local concentration and state of calcium. MATERIALS AND METHODSEnzymes and salt solutions were injected into the slime mold Physctrunz polycephalzmz through a inicropipette. The

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