INITIATION OF DEVELOPMENT IN ARBACIA

Abstract

In I9IO Loeb reported that uninseminated eggs of the California sea-urchin, Strongylocentrotus purpuratus, form membranes while in solutions of SrCl2 or BaC12. Because of the heavy precipitate of BaSO4 which forms on the addition of the latter salt to sea-water, Loeb preferred to use the former. Loeb's work with these salts was done in connection with his experiments on the fertilizing effect of foreign blood and foreign cell extracts. Since this discovery, other workers have investigated the effects of foreign sera, treated in various ways. as agents for initiating development in echinid ova. The present writer also has made a similar study. He has likewise made a study of the effects of precipitates formed in sea-water after the addition of various substances to sea-water alone, in causing parthenogenetic development of Arbacia eggs. It is the latter study which forms the subject of the present communication. The results of the former, however, are also briefly reported. The work was begun at the Marine Biological Laboratory during the summer of I919 and extended during several later years. Some of the precipitates were prepared not only during the summer months but also in April (three different years), in May (four different years), and in September (three different years)i.e., several weeks before the beginning and in the last days of the breeding season of Arbacia. In order to obtain results as far as possible beyond question, I repeated all of the experiments of previous years during the season of 1928. The data here given represent those collected during that year.