-ill- included Ujelang Atoll. Plankton from three stations between the latter contaminated body of water and Eniwetok did not exhibit the wi85 peaks. The third area where plankton was found to contain wi85 was east and southeast of Bikini Atoll and included Rongelap Atoll. The results of ion-exchange chemical separations for all radioisotopes on four plankton samples, two fish tissue samples, and the gamma curve analyses for eight plankton samples are shown (Table 1 and Fig. 3). In Table 1, the dis- integration rates of the plankton are given. In plankton samples from stations 36 and 3, wt55 contributed 60 per cent and 83 per cent respectively of the total radioactivity. These samples did not contain ue7 nor was it detected in any plankton sample containing W 185 | which wi55 was absent, elements Co, Fe, In the plankton samples in the radioisotopes of the transition and Zn and the fission products Bal4o_y_140 contributed almost all of the radioactivity. The gamma spectrum analysis for wt85 in those plankton samples containing the isotope is shown at the bottom of Table 1. The highest levels of wi85 were found in plankton samples from stations 38 and 39. In Table 1, the disintegration rates per ml of plankton