nl. R.B.R. Perssc 12. Health Physics 16, 69 ( 39). C.D. Jennings, Iron-55 in Pacific Ocean Organisms, Ph.D. ‘Thesis, Oregon State Univ. (1968), 77 p. 13. E.E. Held, Pacif. Sci. 14, 18 (1960). 14, 15. E.P. Hardy and J. Rivera, HASL Tech. Rep. 193 (1969), p. II-9. J.P. Tully, in Studies on Oceanography, K. Yoshida, Ed. (Univ. of Wash. Press, 1965), pp. 68-94, 16. The higher specific activity noted in goatfish liver in August 1963 may reflect more nearly the specific activity of waters at Rongelap Atoll than does the sample of March 1963. Livers from immature goatfish were used in the August specimen, while the March sample was obtained from mature fish. Recent measurements of the specific activity of immature and mature goatfish Liver collected at Johnston Atoll in 1968 showed that immature fish livers contained less stable iron and more Fe per unit wet weight than did livers from mature fish. '.We assume that the immature fish are in the process of forming their iron stores and therefore more nearly reflect the environmental specific activities than do the mature fish whose iron stores are already formed. In the latter case, exchange rates may be slow. ‘17. T.W. Duke and T.R. Rice, in Proceedings of the Gulf and _ Caribbean Fisheries Institute, J. Higman, Ed. ‘Miami, 1966), pp. 59-67. (Univ. of