Polyadenylic acid rich RNA has been isolated from sea urchin zygote polyribosomes by oligodeoxythymidylic acid-cellulose chromatography. It is proposed to translate this poly A rich RNA in vitro in either a Krebs 11 ascites or rabbit reticulocyte system. The products of the in vitro synthesis will be identified by a double antibody precipitation method. Using these procedures as the assay system, the sea urchin egg will be fractionated into subcellular components and the untranslated m RNA will be located. It will then be possible to study the mechanisms of m RNA storage and activation in this system. It is also proposed to examine the relative activities of egg and zygote protein synthesis initiation factors and to test for factor specificity. These studies may indicate a possible regulatory role for initiation factors in the protein synthesis activation phenomenon.