- 45 pared with that of northern Rongelap. The fish utilized for food by the terns are small (one to two inches in length) and travel in schools in the open waters of the lagoon. A satisfactory method of obtaining samples of these animals has not been found, other than that of taking them from the gastrointestinal tract of the birds. Tern eggs were collected in October 1955 at Labaredj and Kabelle Islands. Previous collections had been made at Kabelle on July 16, Decem- ber 8, 1954, and January 29, 19555. The levels of radioactivity in both the shells and yolks of eggs of the last collection were low, approximating those found in the bones of terns from the same area. In contrast to the logarithmic decline and decay curves observed for tern bones, radioactivity in the egg shells declind! semilogarithmically with an 80-day halflife; the decay curves also exhibit semilogarithmic decrease with time but contain two components, one with a 50-day half life and the other with a 300-day half life. The rate and type of decline for the egg yolks cannot be determined because of the great variability in the average values for the various collecting dates. Plankton The equipment and methods for obtaining the October 1955 plankton samples were the same as for the previous Rongelap collections, except