Water The water samples collected in Nansen bottles were transferred to polyethylene bottles for storage until analysis. Only half of the samples from each station could be analyzed immediately aboard ship because of limited facilities. Therefore, alternate samples from the 12 Nansen bottles were analyzed at the time and the others were analyzed later in the course or in the New York laboratory. All the samples from the intermediate stations were analyzed immediately, while the surface samples taken with each BT measurement were analyzed in port, or upon return to the United States. The analytical procedure suffers from poor counting statistics for most of the samples taken. Therefore, a high degree of confidence cannot be placed in individual samples and conclusions should be drawn only on the basis of the broad pictures involvingthe average of manysamples. Thecomplete water dataare givenin Appendices B and C which cover the surface samples and Appendix D which covers the samples taken at various stations. The calculations show some negative values, that is, the sample count was less than the current background count. In all cases, these negative values have been used in averaging. As Miyake showed, most of the activity in sea water samples is due to material in solution. Although the zooplankton activity appears to be 300 times the activity of sea water per unit weight, the zooplankton organisms are present in great dilution (2 to 56g per 106 liters on Troll stations) and the Nansen bottle is a notoriously poor sampler of zooplankton organisms. Filtration of 83 sea water samples through a Millipore filter (0.5-4 pore size) showed on the average 9.6 percent of the activity re- tained by the filter. This activity can probably be attributed to microphytoplankton organisms which do not evade the Nansen bottle and appear to have a very high specific activity. The average surface activity along the entire track was 93 d/min/liter, with a maximum of 450 d/min/liter. Low values were found on the return trip from Japan, the average for 29 values between Yokosuka and Midway being 49 d/min/liter, the Table 1 Distribution of Activity in Sea Water Surface Samples* Station Samples** No, of No. of Stations Values Average Values Average Region 4-15 16 17-21 22-27 28-31 32-33 34-38 39-40 41-44 45-46 109 9 46 63 48 24 54 17 45 15 49 72 118 115 107 134 146 166 45 13 144 11 60 71 48 24 60 24 48 24 64 88 95 110 72 74 89 70 45 40 North Equatorial Transition Dubious North Equatorial Counter Current North Equatorial Kuroshio Cold Area Kuroshio Cold Area Total 430 93 514 78 *All surface samples at stations and BT stops, **kDepth samples to 600 m, l2 per cast, * *&