which includes smali fish, invertebrates and algae. Tabie 2 contains data on the rate of decline of the beta radioactivity . in reef fish collected at Rongelap and Ailinginae 26, 1954 and July 18, 1957. Atolls between March The rates of decline in liver, bone and muscle tissue of fish from Kabelle Island are given in Figure !. The decline rates are similar for all three tissues, especially during the first two years. Recontamination by other nuclear devices during the summer of 1956 is indicated by the increase of radioactivity in muscle and bone and a temporary decrease in rate of decline in liver tissue. At present, the radioactivity in liver tissue appears to be declining at a more rapid rate than in bone or muscle, while the radioactivity in the viscera or stomach contents has declined more rapidly than that of other tissues (Table 2) It has been suggested (Welander, 1957) that some of the long-lived isotopes may be accumulating in the bone and muscle fish, whereas the radioactivity in liver tissue is similar of to that in the stomach, bearing out the fact that the liver is an organ for the temporary storage and passage of food and waste products. Itigs of interest to note that the levels of radioactivity in the bone and muacle are about the same as those of the 1955 samples. Data on radioactive decay were obtained from bone and liver tissue of groupers (Epinephalus merra) from Kabelle and Rongelap Islands, and from homogenized muscle tissues from 13 species of reef fish. The decay rates of muscle and bone Figure 1) are more rapid than decline rates for the