The Tension at the Surface of Marine Eggs, Especially Those of the Sea Urchin, Arbacia

Calculations from the centrifugal force necessary to pull an Arbacia egg into two nearly equal parts, a yolk half and a clear half, indicate that the tension at the surface for 25 per cent increase in area is less than 0.2 dyne per cm., with considerable variation in different eggs. Similar calculations based on the force necessary to pull an oil spherule away from the remainder of the egg give maximum values of 0.33 dynes per centimeter for Chaetopterus, 1.1 dynes per centimeter for Illynassa and 0.54 dyne per centimeter for Cumingia.