-22- of plankton as determined in methane-flow counters has been reported on the wet basis so that the specific pared with that of other substances. water uniformly from the plates. activity of plankton may be com- This involves attempting to drain the plankton samples at the time of preparing The varying water content of the planktonic organisms causes uncertainty in evaluating the amount of wet plankton being radioassayed. It was shown (UWFL-53:19) that if results were based on the amount of planktonic ash rather than on the amountof wet plankton, the variability in radioactivity of replicated tows was reduced to only one half the value obtained on the wet basis. Similarly, the present data for Rongelap Atoll were more consistent on an ash than on a wet basis. The greatest disparities between the two values for paired tows occurred in the 1956 collections, as seen in Table 3. At Kabelle Island, the ratio between the two values was onl: 3.6 on the ash basis, but 8.9 on the wet basis, only 4.3 ash basis, but 8.6 wet basis, so that and at Rongelap Island here, as at Eniwetok Atoll, the variability is only half as great on the ash as on the wet basis Further, the average level of activity in plankton from Ailinginae lagoon in October 1955 was noted (UWFL-43:46) to be higher than in Rongelap lagoon on the wet weight basis. But if the unit of ash weight instead of wet weight is used, radioactivity per the Ailinginae levels are no higher than in Rongelap lagoon near Kabelle Island (Table 3).