Abstract
The X-ray inactivation of Arbacia punctulata fertilizin reported by Richards and Woodward (1915) and by Evans, Beams and Smith (1941) is confirmed. Further data on this inactivation are presented in terms of Roentgen units, fertilizin conc, and sperm conc. U.V. light was found effective in the inactivation of Strongylocentrotus purpuratus and Lytechinus anamesis fertilizin. Arbacia sperm, after treatment with fertilizin which had been almost completely inactivated by X-rays, showed the same resistance to subsequent agglutination by untreated fertilizin as did sperm which had reversed after treatment with unirradiated (control) fertilizin. Strongylocentrotus and Lytechinus fertilizins whose sperm agglutinating powers had been completely destroyed by u.v. light likewise retained their original sperm combining powers, as indicated by their ability to render sperm non-reactive to untreated fertilizin. Tyler''s (1941) view that fertilizin may be converted to a non-agglutinating "univalent" form is considered the most reasonable explanation for the results. Thus, X-rays and u.v. light are 2 new agents for the production of univalent fertilizin.