-2l- of ubout 0.3 ina fish (Tilapia). and scales, however, In the case of fish bone the concentration factors may be higher. In the croaker (Micropogon undulatus) concentration factors for strontium in vertebrae and scales were 2.5 and 2.1 respectively those of sea water. In addition to the above mentioned factors, isotope dilution by stable strontium would result in reduced uptake of Ssr99 by marine organisms. Stable strontium is present in the sea at a level 6 to 1300 times that of the naturally oc~ curring forms of the other elements represented in fallout (Table 3, column 2). Thus the discrimination against radio- strontium as &@ consequence of the presence of stable stron- tium in sea water would be 6 to 1300 times that to which the other radioelements would be subjected because of the presence of their stable counterparts. Further discrimination against the uptake of radiostront ium in these organisms may be caused by the scavenging action of calcite formed from coral aragonite in fallout material. simple experiment by the author, pulverized coral was. In a sprinkled onto and allowed to settle through sea water contaminated with sr 39 Clo. Approximately 11 per cent of the radionuclide removed from solution the first hour. was noted in @ parallel was No reduction in actARCHIVES control experiment. Suito, Takiyama and Uyeda (22) reported that the ashes from the March 1, 1954 weapons consisted test at Bikini of white which fell on the granules of calcite No. 5 Fukuryu Meru approximately