-18- compared with that in algse and found to be quite similar as would be expected in a species which is principally herbivorous. The decline in the radioactivity of sea water is included on a different scale to indicate the dependence or similarity in the trends. Algae are dependent on sea water for their radio- activity, which they concentrate up to several thousand times (Palumbo, 1957). The surgeonfish take in considerable amounts of radioactive material by feeding on the algae. The data from Belle Island (an area in which the supply of radioactive mater{al is only slowly decreasing) indicate that, for every micro- curie of radioactive material ingested into the alimentary tract, about 0.55 microcurtes are distributed to the skin, muscle, bone and liver combined. In Figure 6, the decline of radioactivity in the liver tissue of omnivorous fishes is compared with that of the sea cucumber gut contents (Bonham, 1957) and algae. The similarities appear to be marked during the early pertod of decline, with liver tissues of omnivorous fishes and sea cucumber gut averaging greater amounts of radioactivity than algae at 531 days. Sea cucumber gut content is made up mostly of coral detritus, since this invertebrate obtains its food from this material. Coral fragments are also found abundantly in the alimentary tract of the mullet, a detritus feeder, along with plant and animal material. However, comparisons of the decline in these two or- ganisms in Figures 6 and 10 show marked differences in the trends of radioactivity. It will also be noted that the decline of radioactivity in mullet tissues is considerably different from