MECHANICAL PROPERTIES OF STARFISH OOCYTES*

The stiffness of the starfish oocyte was determined from the degree of deformation when it was compressed by a definite force between a pair of parallel plates. The deformation of the oocyte increases during continued application of a constant force, indicating visco-elasticity of the cell. A cyclic change in stiffness of the oocyte accompanying meiotic divisions was found: the stiffness of the oocyte decreases during early stage of meiotic division, increases before the onset of the first polar body formation, then decreases, increases again before the onset of the second polar body formation, and decreases thereafter. Deuteration causes increase in stiffness of the oocyte.