internal methane gas-flow counting chambers at the Laboratory of Radiation Biology in Seattle. Counts per plate were converted to disinte: grations per minute per gramof wet tissue by correcting for sample weight, geometry, backscatter and self-absorption. For a more complete discussion of these procedures see Donaldson et al. (1953). Other tissues were treated similarly, with the exception of liver,in which case the whole organ was removed from each specimen. Ifa suf- ficient number of specimens of a single species was obtained, the tissues were treated separately as in the case of goatfish and halfbeak from Kabelle Island (see Table 1). Decay rates for radioactivity of tissues of fish collected in 1956 were calculated because there were indications that Rongelap Atoll was contami- nated during the Redwing operation. Gamma spectra and total gamma counts were made on dried or ashed Samples in a single channel, 50-position, automatic advance, gamma spectrometer using a two-inch, well-type sodium iodide crystal. Chemical analyses were made by ion-exchange resin column and radiochemical pre- cipitation techniques The radioactive isotopes contained in the separate fractions were identified by determination of the gamma energies, beta mass absorption studies using aluminum foil. and by Correction factors for converting beta and gamma counts to disintegrations per minute were calculated by the use of standards of known energies. Details of the procedures used are given by Lowman et al. (1957). oO oF AS ys