10 Summary Marine organisms were collected on May 16, 1948, from the shallow waters of the reef about one and one-fourth miles north of Runit Island for the purpose of determining the beta~gamma radiation. Samples of about one gram wet weight were reduced to an ash for counting. In the fish samples the skin, miscle, bone, liver, gut, and gills were sampled. was used as a sample. The entire organism for most invertebrates A total of 118 samples were prepared and counted. The greatest concentration of active material was found in the gut but some distribution of radioactive elements to the tissues had started in the short time (one and one-half days) between the fall-out and time of collection. Decay studies on selected samples show a very rapid rate of initial change. A straight line fitted to the last three points in the decay curves, i.e. for November 27, 1948, Jamuary 1, 1949, and Februery 19, 1949, give a half life period of approximately 180 days. UNIVERSITY A-te ES IES UNIV. OF WAS. LIGIAR 2 uae ane o ‘ te _ UN: Au Cus ES a ys = ey TAT tt