THE EFFECT OF HYDROGEN ION CONCENTRATION UPON THE INDUCTION OF POLARITY IN FUCUS EGGS

Abstract

When a Fucus egg develops near one end in a close fitting capillary tube of pyrex glass or silica (quartz), diffusion of substances passing to and from the egg is more impeded on the side of the egg towards the far end of the tube. The egg therefore develops in a gradient of its own diffusion products, and of O2 tension. When the medium, which is initially homogeneous inside and outside the capillary, is initially at pH 6.5-7.6, nearly all of the eggs develop rhizoid protuberances on the sides of the eggs toward the far end of the capillaries. This is on the sides of the eggs where the conc. of substances diffusing from the eggs is greatest. The polarity and developmental pattern of the egg is thus detd. either by a concn. gradient of products diffusing from it, or by a gradient of O2 tension. The former interpretation is favored. When the medium is made more basic, the percentage of the eggs which form rhizoid protuberances toward the far end of the tube decreases to about 20-25% between pH 9.1 and 8.6. The response of the egg to the gradients which it produces is thus statistically reversed. The determination of the polarity of the eggs by the diffusion gradients does not become as complete in alkalinized as in acidified sea water.