-16- In general, the gamma spectra of the fish tissues from different areas have definite similarities, even when compared to results ob- tained from other atolls (Lowman et al. 1957). Differences in gamma spectra appear to be greater between different organs of the same fish than between the same organs of fish from different islands or atolls. Separation and Identification of the Nuclides by Ion-exchange Techniques To identify the various radionuclides contained in the reef fish liver samples collected at Enibuk Island, Ailinginae Atoll, July 11, 1957, the samples were pooled and the ash (0.384 grams) dissolved in 0.2 N HCl. This solution, after filtering, was passed through an ion-exchange cationic resin column of Dowex 50. The anions and HCl wash fractions of the sample were combined and later passed through an ion-exchange column of Dowex 1 anionic resin to further separate the fractions and to obtain the excess of the nuclides resulting from overloading the cationic resin. The radioassay of the fractions obtained from both columns is summarized in Table 5. Details of these procedures have been reported by Lowman et al. (1957). The methods generally follow those developed by Tompkins et al. (1947), Kraus and Moore (1953), Kimura etal. (1956), Takanobuet al. (1956), and Ishibashi et al. (1956). The identification of Fe°° in the oxalate fractions was made by mass absorption technique in a windowless methane gas-flow beta counter. One-m] plates of several fractions totaled 39 c/m after drying under an + OF *! a: 1