ELECTROPHORETIC MOBILITY OF SEA-URCHIN EGGS DURING THE DIVISION CYCLE

The electrokinetic potential of fertilized sea-urchin eggs, without the fertilization membrane and hyaline layer, was investigated by measuring the electrophoretic mobility of the eggs from fertilization to the second cleavage. A cyclic change in mobility was found to accompany the division cycle: the peak of the change was observed about 15 min before the appearance of both the first and second cleavage furrows. A smaller peak was observed at 20-30 min after fertilization, but such a peak was not repeated between the first and the second cleavage. Fertilized eggs with the fertilization membrane intact did not show a significant change in electrophoretic mobility throughout the division cycle.