Action of trypsin on the eggs of Dendraster excentricus

Crystalline trypsin in 3 × 10^?8 M concentration and higher, elicits fertilization membranes in the unfertilized eggs of Dendraster excentricus. These membranes are adequate in artificial parthenogenesis. If the action of trypsin on these eggs is continued for two or three hours the result is first, digestion of the membranes, followed later by reduction of the egg to amoeboid form. When fertilized, some of the partially digested eggs segment and form irregular cell masses, thus demonstrating that, in response to trypsin, there is first the cortical reaction giving rise to the fertilization membrane, and second, the progressive digestion and disintegration of the cytoplasm.Chymotrypsin causes rounding of the unfertilized eggs and, in rare instances, a few membranes, but the enzyme is not an adequate parthenogenetic agent.Fertilization of the egg renders the cytoplasm resistant to trypsin. The facts lead to the suggestion that fertilization liberates trypsin inhibitors in the cytoplasm.