-19- for this group of radioelements. This observation is in agreement with the findings of the Taney survey (10) in which the major fission products in plankton were found to be Celt4-ppl 44, However, & gamma spectrum curve made on these plankton samples November 1957 by the present author revealed an appreciable amount of Co, zr95-Np95 were not found in the Taney samples because of the short half life of Zr99 (65a). In the case of the non-fission-product radioelements, zinc, cobalt, and iron were present in the plankton (based on an average of the five samples) in approximately equal amounts at about 24 per cent each and manganese at a level of less than one per cent of the other three elements. of these elements, from fallout in the sea, All would exist initially in the insoluble form. Limited data from both control experiments (4) and field observations (21) suggest that the major route for uptake of fallout radiolsotopes by marine animals is through the ingestion of radioactive particles. also that, Chipman (5) noted in addition to the filter feeding animals, two species of algae were able.to concentrate Celts severe] poe ARCHIE” thousand times over the levels in the water although the radioisotope was in the particulate form. is The present work in agreement with the postulate that the major source of radioactive elements from fallout to marine zooplankton is through the uptake of particulate material. The uptake may 24