distance of sample from test site. For stations nearest the test site, values for the post test samples were several hundre d times greater than for the pre-test samples. Since the counts of “Fe(0H)3 scavenge” and "Ca-Sr oxalate" do not equal the count of “whole sample" evidently all of the radioactive materials were not removed by these processes. A rain water sample was colleeted 33 hours after the Mike shot in the lagoon off Eniwetok Island. A 4%50-ce sample was evaporated and counted on November 4, 87 hours after Mike, using a Victoreen survey meter with a one-inch end window tube, window thickness 1.8 mg/cm“. The maximum count vas 10,000 per minute. 4.2 Plankton The plankton nets were 4+ meter in diameter and 2 meters long. The anterior section was cylindrical, the posterior section conical with a detachable net end. The plankton tows were made in pairs, at the surface and during daylight hours. One net of each pair was constructed with No. 6 silk (74 meshes per inch) and the other of No. 12 silk (173 meshes per inch). Towing time was usually one hour and the distance towed was about 14 miles. Catches of plankton were small. Exclusive of jelly fish the greatest volume of plankton in a one-hour tow was 28 cc. This value was obtained by decanting and measuring the preservative and then subtracting this amount from the volume of preservative and plankton. A gross examination of the types of organisms present ~ 2D ~