ABSTRACT The pattern of changing levels of radioactivity is given for the tissues of land hermit crabs, Coenobita perlatus, from Belle Island, Eniwetok Atoll, during a period of nearly two years following the 1954 series of atomic tests. gpI, y?, and csl37 were the principal long-lived fission products found. gr9° levels in the skeleton remained constant throughout the period of study. ACKNOWLEDGMENTS The wholehearted cooperation of all members of the staff of the Applied Fisheries Laboratory, who at various participated in the collection made this report possible. times and preparation of samples, Miss Dorothy J. South supplied the results of the radiocesiun, radioceriun, and some radioStrontium determinations. The cooperation of the U. S&S. Atomic Energy Commission Division of Biology and Medicine and the Eniwetok Field Office, Task Group 7.1, and Holmes and Narver | Or te greatly facilitated the field collecting. “4 eA 4 . 4 . RRS woa "