bone, 8.7: 1; and liver, 8. 4:1. The decline curve for shore bird bone is logarithmic and similar to that of the tern bone (r = t72-5), The variability in the muscle and liver samples from the shore birds precludes the drawing of decline curves for these tissues. In the January 26-30, 1955 collections��� , the northern Rongelap terns from Gejen, Kabelle and Labaredj Islands were found to contain less radio- active material per unit weight than did the terns from the southern island of Rongelap. This finding was unexpected because of the fact that the aver- age levels of radioactive contamination were higher in the northern than in the southern islands. Because the Rongelap natives usually collect birds at Ailinginae Atoll, seven and one-half nautical miles to the southwest of Rongelap Atoll, and in view of the observation that the southern Rongelap terns were more radioactive than the northern Rongelap birds, collections of terns were made at Ailinginae Atoll on October 23, 1955. The ratios of Ailinginae Atoll tern tissues to north Rongelap Atoll tern tissues are as follows: muscle, 1.9:1.0; bone, 1.9:1.0; liver, 2.0:1.0. Thus the Ailinginae terns contain, on the average, about twice as muchradioactivity as the terns from tle northern islands of Rongelap Atoll, although the general level of contamination at Ailinginae is much lower than in the north end of Rongelap. Inasmuch as these birds are predominantly fish eaters, the higher levels of radioactivity in the tissues of the southern birds suggest the availability of 4 supply of food fish with a higher average radioactive content in the southern area com-