PHYSIOLOGICAL ANALYSIS OF THE CORTICAL RESPONSE OF THE SEA URCHIN EGG TO STIMULATING REAGENTS. I. RESPONSE TO SODIUM CHOLEINATE AND WASP-VENOM

¹ The Sugashima Marine Biological Station of Nagoya University, Sugashima, Shima-gun, Mie-Ken, Japan

1. The formation of the fertilization membrane in Hemicentrotus eggs can be induced by an appropriate treatment with sodium choleinate or wasp-venom. When the concentration is optimum, the membrane begins to rise in one or several regions of the egg surface and several minutes are required to complete its full elevation.

2. If the eggs are washed with sea water when elevation of the membrane has occurred only locally and not over the whole egg surface, the membrane formation is interrupted. The cortical granules have been broken down only in the part of the egg cortex where the membrane is separated while they are intact in the remaining areas.

3. These results constitute the evidence for the conclusion that the breakdown of the cortical granules itself at any point does not become the cause of the breakdown of the neighbouring granules. It seems to follow, therefore, that some invisible cortical change of a propagating nature must occur in order that the cortical granules be broken down at the time of fertilization. This invisible cortical change may be called the "wave of fertilization" or the "fertilization-wave," since it resembles Yamamoto's "fertilization-wave" in Oryzias eggs.

4. It is suggested that sodium choleinate and wasp-venom cause the breakdown of the cortical granules without intervention of the fertilization-wave.