The movie shows two sequences that begin with an unfertilized Arbacia (sea urchin) egg in which the contents have been stratified using the centrifuge polarizing microscope (CPM) developed by S. Inoue. The main feature seen with the polarizing microscope is the appearance of a negatively birefringent layer of stacked membranes. Sperm are then introduced. A few seconds after sperm entry, this birefringence disappears as stacked membranes fragment. The egg also becomes lighter and rises.