300 mg, 4.0; 600 mg, 5.2; and 1100 mg, 6.9. The average self-absorption correction factor from 135 randomly selected plates was 2.23 7 0.023. Total correction factor for 68 pre-test samples was 4, Sere an eae votre 3.93 7 0.21, and for 64 post test samples was 5.98 7 0.62. RESULTS AND ANALYSIS OF DATA The reliability of the results of certain average values as used in this report to express the radioactivity of a group of organisms is subject to the following considerations: (1) Non-random selection of specimens. In the field, collection of specimens was directed towards obtaining certain species at all stations, if possible, and supplementing this collection with whatever other species were available. When & large number of a single group of organisms was available only a small percentage of the specimens was collected, whereas all of the specimens may have been collected for another group of organisms which were less abundsnt. Hence, the speci- in the field collection and also in the samples used for counting. (2) Random selection of tissues. In some instances the activity of pre-shot invertebrates for a collecting station was estimated by averaging all the samples counted irrespective of tissue or species. Such an estimate is an average of Plate counts and not an average of the pre-shot invertebrates. - 17 woud ayers allibteiatione at aan ee mens are represented qualitatively rather than quantitatively HOE ARG DEVES