their contractors, have partially knowledge, these "spot checks" leave much to be desired However, filled in the gaps in our in completing the story of radiation contamination in biotic materials following an atomic bomb burst. The order of magnitude of a complete study of biotic contamination in a field-testing area is very great, but the data to be obtained are of such extreme importance that it is worth any amount of effort which may be expended to attain this information. The amount of fission products in the mud at the bottom of the target area of Bikini Lagoon has been calculated at 2 x 10° curies?, a week after the explosion. By 1947 the radiation had apparently disappeared from the water, but hydroids growing on floats anchored in the lagoon picked up radioactive materials so that when they were counted on January 14, 1948, recorded 1,700 counts per minute per gram of dry weight material@, In the bottom of Bikini Lagoon near the target area coralline algae (Halimeda) dredged from the bottom in August of 1949 and counted November 6, 1951, produced counts varying from 1,868 to 10,325 with an average of 8,342 counts per minute per gram of ashed material. lfhe Effects of Atomic Weapons, U. S. Government Printing Office, Washington 25, D. C., June 1950, p. 283. 2collected by the Applied Fisheries Laboratory resurvey group, August 1947; counted January 14, 1948,--245 counts per minute per gram; counts made with an end window counter of approximately 15 percent geometry.