- 65 - Bikini-Eniwetok test site has provided a variety of radio{isotopes that become biological tracers for field experiments in mineral metabolism, valuable information has been acquired on the distribution of many elements in the marine biota. However, to understand the transfer processes and the piological effects of radiation, experiments under controlled laboratory conditions are required. Conversely, results of laboratory experiments that are to be extrapolated to the natural environment require field testing. Many of the observations by the staffs of the Laboratory of Radiation Biology, University of Washington, Seripps Institution of Oceanography, and the Naval Radio- logical Defense Laboratory on the uptake of radioisotopes by marine organisms in the natural environment have been verified and supplemented by the laboratory experiments of the Radiobiological Investigations of the Bureau of Commercial Fisheries and the Hawaii Marine Laborator, University of Hawaii. For example, Lowman (1956) and Schaefer (1958) have reported from field observations and Chipman (1959) from laboratory experiments that zooplankton rapidly accumulate radioactive particles. Chipman states that when the radioactive particles are no longer available, the zooplankton soon lose their radioactivity. Oysters,