For some of the fish the total activity of individuals was determined, not by randomly selecting by tissues, but by using weighted samples of all tissues. group The activity of the (fish) was then determined by averaging the values for the individuals. Although the two methods for determining the group average differ in the degree of refinement of the data, one viewpoint is that the method used for the pre-shot invertebrates adequately describes the trends and that for these organisms further refinement is not warranted because of the nature of the errors in the data. (3) Variance of sample counts. Variance both within groups and between groups was often great. The greatest var- jance and also the highest specific activity were found in th those tissues with radioactivity from “surface” contamination, e.g., algae in the digestive tract of fish, sand in the gut content of the sea cucumber, algae growing on the carapace of the crab, or fallout particles on the surface of land plants. On the other hand the radioactivity of tissues with absorbed isotopes only, such as muscle, bone and liver, was less varusually fable and was/lower. Consequently, it is believed that the greatest cause of variance in the sample counts was due to the amount and type of food in the digestive tract and/or the materials on external surfaces. (4) Number of items in a sample. Small samples resulted from breaking down the collection into small groups such as Species. The combination of a few samples and a large value - 18 - OR he HIVES