paul ile ell , ~2i- and Co®9 about 28 per cent, and Fe°5 about 26 per cent. The radioiso- ‘tope Mn was detected in Only minor amounts and unidentified radioisotopes amounted to about 6 per cent of the total radioactivity. It was presumed that the unidentified radioactivity was due to beta particles which penetrated the aluminum shield of the sodium iodide crystal. However, these totals may be conservative, due in part to sample loss and partly because all of the gamma activity was not accounted for. It will be observed that almost all, if not all, of the radioactivity ig due to non-fission products (Table 7). It is also of interest to note that since the discovery of Zn®5 in tissues of fish from the Pacific area by Kawabata (1954), this radioisotope has consistently been found in fish tissues, usually as the dominant radioisotope (Rinehart et al., 1955; Donaldson Mori, et al., 1955; Yamada et al., 1955; Saeki, Okano, and 1955; Mori and Saiki, 1956; Yoshii, 1956; Nagasawa etal, 1956; Lowman et-al., 1957). There are additional similarities in the kinds and amounts of radioisotopes found in fish tissues. Most investigators have found little or no radiostrontium, even in the bones of fishes. Radioisotopes of cobalt have been found in tissues of fish from Bikini and Eniwetok Atolls (Lowman et al., 1957) as well as in fish of the open sea (Kawabata, 1954). Co?! Co%8 and C060 together, comprise as much as 28 per cent of the radio- activity in the fish tissues of the Rongelap area. Fe°5 and Mn°4 have both been found by previous investigators (Lowman et al., 1957). Apparently am, PLTSs