A model of cell cleavage.

A model is presented which describes, at least to a first approximation, the oserved changes in cell shape and the movement of surface markers associated with cleavage in some types of cells. The model postulates that the constraints governing cell cleavage are minimum surface area and constancy of cell volume. Equations are derived both for the case of symmetric as well as the case of asymmetric cleavage. It is pointed out that the generally symmetric character of cell cleavage is explicable if there is a positive correlation between internal cell pressure and the radii of curvature.