The Physical Structure of the Protoplasm of Sea-Urchin Eggs

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Abstract
Physiologists have usually compared protoplasm to various lyophilic colloids. The interior protoplasm of the sea-urchin egg is a suspension of visible granules, and its colloidal behavior should be interpreted on this basis. In these eggs the viscosity of the suspension medium and that of the entire suspension have been determined. The viscosity of the suspension medium, relative to water, is roughly about 2, whereas that of the entire protoplasm is 4 or 6. Factors responsible for changes in viscosity include alterations in the properties of the granules and their surfaces, and alterations in the suspension medium. A possible hypothesis is that the granules of the protoplasmic suspension are surrounded by a lipoid film. The viscosity data fit this hypothesis, and tests with osmic acid support it. It is inferred that the suspended particles bear a positive electric charge; at the surface of the egg the charge is negative.

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