THE OCCURRENCE AND DISTRIBUTION OF RADIOACTIVE NON-FISSION PRODUCTS IN PLANTS AND ANIMALS OF THE PACIFIC PROVING GROUND Introduction After the detonation of the Castle series of nuclear devices in 1954, fission product chemical separations were made on several organs and tissues of yellow snapper (Lutianus vaigi- ensis) and mullet (Neomyxis Chaptalli and Chelon vaigiensis) collected at Edna Island, Eniwetok Atoll, on July 3, 1954. In addition, the levels .of cad in the samples were determined. The total activities contributed by non-fission products were as follows: Per cent of activity contributed by non-fission products Organism Bone Muscle Skin Liver Gut Yellow snapper 99.0 98 .0 86.2 95.8 50.5 Mullet 75.3 95.1 83.8 91.4 These results, in conjunction with radioactive decay data, 0 8 -absorption and indicated the presence of large amounts of non-fission isotopes in the fish samples. In addition, the levels of non-fission products were higher in each instance in the carnivorous fish (yellow snapper) than in the detritus feeder