Studies of the ultrastructure of sea urchin eggs and the changes induced at insemination

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Abstract
Eggs from 16 species of sea urchins were studied in the electron miscroscope. The jelly coat was present in several of the species, and a hyaline layer was observed between the jelly coat and the actual surface of the egg. As an inner boundary of the jelly coat a membrane was often present. The structure of the cortical granules appeared to be species-specific, and its possible use as a taxonomic character is discussed. At insemination the cortical granules were observed to break down completely before the formation of the hyaline layer and the fertilization membrane. As the events following insemination seemed to be the same for all the species studied, the actual structure of the cortical granules cannot be of importance for these processes.