and organ or tissue being considered. When compared by rank- ing within each of the nineteen classes of items in Table 8, the stations fall into the following decreasing order of radioactivity: Japtan. Bogallua, Engebi, Aaraanbiru, Rigili, Runit, Igurin, The giant clam, Tridacna, was the only species col- lected at every station. Comparison of individual tissues of this clam at each station is made in Figure 5. The specific activity relative to Igurin is shown for gill, mantle, muscle, and digestive gland ("liver"). Whichever tissue is considered, the ranking of the stations remains the same. Japtan is not included since several of the counts were background, hence the ratios are meaningless, and the relative activity was in every case less than one. Included in Figure 5 are the rela- tive activities of beach sand or soil and bottom sand from each station. The latter has 4 higher relative, specific activ- ity at Engebi than at Bogallua while the reverse is true with the giant clam tissues. No landing was made at Bogallua, con- sequently no beach sand is available from that station. Bot- tom sand was taken from sea cucumber guts, usually Holothuria atra. This can be considered a random sample of the bottom sand since H. atra shows no selectivity in its ingestion of bottom materifals.3 This difference between Engebi and Bogal- - 37 -