THE CONDITIONS OF ACTIVATION OF UNFERTILIZED STARFISH EGGS BY THE ELECTRIC CURRENT

¹ University of Chicago and Marine Biological Laboratory

1. A new type of non-polarizable (Zn-ZnSO₄) electrode of low resistance is described by which strong electric currents (up to 2 amperes or more) can be passed for prolonged periods through a small quantity of sea-water without appreciably affecting its composition.

2. It was found that unfertilized starfish eggs can be readily and completely activated by moderate currents, of the density 200-300 milliamperes per square centimeter; but that the effect in such cases is due almost entirely to the heating action of the current on the sea-water. When the temperature is kept below 29° such currents produce little or no effect upon the eggs. Unfertilized eggs are thus insensitive to the current as compared with most irritable or active cells of other kinds.

3. When the eggs are exposed in a stream of running sea-water to stronger currents (6000-800 ma./cm.) for brief periods ( to 2 minutes), definite effects are produced. The eggs undergo marked deformation during the passage of the current, and a variable proportion afterwards show fertilization-membranes and partial activation. Complete activation of a large proportion of eggs was not possible in our experiments, although a few developed to the blastula stage.

4. We conclude that the unfertilized starfish egg is insensitive to currents of moderate intensity, and exhibits activation only when currents are used of such intensity as to produce definite and well marked structural changes in the egg-system.

5. Similar exposure of unfertilized sea-urchin eggs (Arbacia) to strong currents, with and without after-treatment with hypertonic sea-water, gave inconstant or negative results.

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