Contrary to expectations Ca 45 occurs in the radio-~ active materials from Eniwetok. / from the shot islands: Samples obtained after the last tests have up to 65 percent of the activity from calcium. Further Study of this element in the field is important because of its abundance, long half life and relation to living crganisms. Small amounts of any radioactive material in a water environment are of greater importance from a contamination standpoint than like amounts on land. The ease with which they are transported in this mediun, with a greater chance of being taken up by living organisms,results in a monitoring problem which cannot be effectively measured with field-type monitoring instruments. 2. What advantages have field studies over laboratory studies? Laboratory experiments in themselves cannot substitute for direct observation in the field. studies, The field where the entire balance of interrelations of faunal and floral systems is involved, presents 7 U. S. Atomic Energy Commission report, UWFL-23 the (AECD-3446).