ELECTROKINETIC STUDIES OF MARINE OVA. V. EFFECT OF PHCHANGES ON THE SURFACE POTENTIALS OF SEA-URCHIN EGGS

¹ Misaki Marine Biological Station, Misaki, Kanagawa-ken, and Zoology Department, Faculty of Science, Tokyo Imperial University, Tokyo

1. No isoelectric points were found in unfertilized eggs of Pseudocentrotus depressus and in both unfertilized and fertilized eggs (with fertilization membrane) of Anthocidaris crassispina when the pH was changed down to 2 in sea water.

2. In all the above cases, the maxima are found in the neighborhood of neutrality. Consequently, in natural sea water (pH, 8.2), the absolute magnitude of the potential is below the highest level.

3. Fertilized eggs carry a less negative potential than unfertilized eggs.

4. The data are discussed in connection with the sperm potentials and their changes in egg water reported by Mudd et al.