ELECTROKINETIC STUDIES OF MARINE OVA

II. CUMINGIA TELLINOIDES, ASTERIAS FORBESII, ECHINARACHNIUS PARMA, NEREIS LIMBATA AND CEREBRATULUS LACTEUS

¹ From the Zoölogical Laboratory, University of Pennsylvania, and the Marine Biological Laboratory, Woods Hole, Mass.

1. By means of the method described in an earlier paper and a slight modification of it, the surface charge of five kinds of marine ova was measured.

2. Cumingia eggs with jelly show a charge of — 34.1 millivolts (23 measurements); eggs without jelly show a charge of — 28.8 ± 0.46 millivolts.

3. Asterias eggs with jelly have a charge of — 19.0 ± 1.04 millivolts; those without jelly — 19.9 ± 1.01 millivolts; and eggs without jelly which were killed by heat have a charge of — 19.0 ± 0.49 millivolts.

4. Echinarachnius eggs with jelly have a charge of — 31.6 millivolts (23 measurements), and eggs without jelly seem to have a charge of about — 20.0 millivolts.

5. Nereis eggs, according to less accurate data, show a charge of about — 10.0 millivolts.

6. In the case of the Cerebratulus egg, the negative charge of the chorionic membrane was first ascertained; next the cathodic migration of the egg cell within the chorion was observed; and finally the surface charge of the cell in sea water was demonstrated to be in the vicinity of zero.