same period; however, liver tissue decay and decline rates are similar. The differences in rate of decay and decline in both bone and muscle may indicate greater retention as well as continued uptake of long-lived radioactive materials in these tissues. Figure 2 illustrates the rate of decline in the tissues of fish from Rongelap Island between January 25, 1955 and July 17, 1957. Again it will be noted that the rate of decline of radioactivity is somewhat greater in the liver tissue than in bone or muscle. All tissues show a definite increase in radioactivity after the summer of 1956, reaching a relatively higher level than for the same tissues in fish from Kabelle Island, but declining at a more rapid rate after 1956. Decay and decline rates of radioactivity of muscle and bone tissue from fish from Rongelap Island are approximately the same, decay being slightly more rapid. The radioactivity in liver tissue declines at a more rapid rate than it decays. Gross Gamma Radioactivity, Table 3 contains 1957 data on gross levels of gamma radioactivity in the homogenate of manyreef fishes collected at Rongelap and Ailinginae Atolls. As with the beta radioactivity, Rongelap Island fish generally had less gamra radioactivity than fish from either Enibuk or Kabelle Islands. Also differ- ences were not great between similar species from different islands. A markedly higher amount of radioactivity was noted again in the liver of pur’ RCH