THE INFLUENCE OF HYDROGEN ION CONCENTRATION ON UNFERTILIZED ARBACIA, ASTERIAS AND CHÆTOPTERUS EGGS

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

A method is described for preparation of CO₂-free sea water of H-ion concentrations from pH 4.5 to 10.2.

The eggs of Asterias, Arbacia and Chtopterus retain for the longest time their capacity to fertilize and to divide at about pH 6.0.

Approximately this same H-ion concentration is required to completely repress the maturation process in Asterias eggs.

Chtopterus eggs are activated by exposures of 30 minutes or more to solutions of pH 5.0 to 6.6. If left in these solutions they show marked ameboid movements and fragmentation, but do not divide. If returned to sea water half or more of the eggs will undergo one or two abortive divisions. The activating effect of the acid sea water is most intense at about pH 5.8 to 6.0.

An exposure of 5 or 10 minutes to solutions of pH 5.0 to 6.6 (which is insufficient to activate) creates a block to fertilization which is permanent if the eggs are returned to sea water. If left from 30 minutes to several hours in the acid sea water, these eggs gradually recover their fertilizability, and when inseminated develop almost normally.