2 oe and Co®® shout 28 per cent, and Fe°> about 26 per cent. The radiocisc- tope Mn°* was detected in only minor amounts and unidentified radio- isotopes amounted to about 6 per cent of the total radioactivity. It wae presumed that the unidentified radioactivity was due to beta particles which penetrated the uuminum shield of the sodium iodide cryetal. 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 is 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 (Rinehartet 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 ———— CI ce eaten ce ‘ ~ 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). Coo? Co°8 and C080, together, comprise as much as 28 per cent of the radio- activity in the fish tissues of the Rongelap area. Fe55 and Mn°‘4 have both been found by previous investigators (Lowmane’ al., 1957). Apparently