THE INFLUENCE OF HYDROGEN ION CONCENTRATION ON THE DEVELOPMENT OF NORMALLY FERTILIZED ARBACIA AND ASTERIAS EGGS

¹ From the Lilly Research Laboratory, Indianapolis and the Marine Biological Laboratory, Woods Hole

The effect of acid and alkaline sea water on the rate of cell division in normally fertilized Arbacia and Asterias eggs was observed as far as the 128-cell stage.

In Arbacia, the velocity of division is reduced to 50 per cent. of the velocity in sea water (pH 8.15) at pH 5.2 and 9.4. Between pH 5.8 and 8.2 these eggs divide normally both in respect to velocity and quality of cell division. Between pH 8.2 and 9.2 the velocity of division is increased from 15 to 25 per cent.

Asterias eggs are more sensitive to both acid and alkaline sea water during the precleavage period than at any subsequent time. When these eggs are transferred to the acid and alkaline sea water immediately after fertilization, the velocity of division is reduced to 50 per cent. at pH 5.6 and 9.2; when transferred in the two cell stage the corresponding limits are pH 5.4 and 10.2. There is a slight decrease in the mean velocity of division between pH 8.2 and 5.8, but no significant increase in solutions more alkaline than sea water.

In both species, when the developmental velocity is reduced below 50 per cent. by either acid or alkali, the nucleus tends to divide without division of the cytoplasm, and abnormal multinuclear cells are formed.