Studies of the species specificity of echinoderms

Abstract

Experiments in which oocytes were inseminated with heterologous spermatozoa showed that Qocytes are susceptible to the same species of sperm, as are the ripe eggs. Immediately after the spermatozoon has entered an egg or an oocyte, material appearing dark in the phase contrast microscope is ejected from the maternal nucleus; a ring-shaped corona is formed around the nucleus. No aster formation takes place in oocytes which have not yet developed the cortical reaction.