When the counting error is >100%, the concentration is The + value is 1 o counting error. reported as <2 0. >21 7,72 6.1 <4.0 24.2+3,1 A >94 mm 2,289 42,28 13.9 42.5 80—94 mm} D 12.14#1,1 D 65—73 mm 0.72 +0.32 6.1 7.7 4.40 +406,90 33.8 +5.4 D 50—64 mm} 3,41 +0.90 39.6 +2.8 0~—49 mm D 2. The activities in carp gastrointestinal tracts are much higher than in carp bodies presumably due to sediment found in the gut. 3. It appears that there is little transfer of plutonium across intestinal walis of carp into body tissues. 4, Crayfish collected downstream of Mound Laboratory show elevated tevels of Pu particularly in soft tissues as opposed to shell, S. Activities of 238py in crayfish tend to increase during an effluent pulse. 6. A size-dependent relationship may exist in crayfish with larger size classes having lower activities per unit weight than smaller size classes possibly due to the difference in relative surface area of the shell and gills. ACKNOWLEDGMENTS The authors wish to thank W. H. Westendorf, D. G. Carfagno and R, Robinson of Mound Laboratory for their cooperation; and J. R, Gammon and C. Yoder of De Pauw University for providing us with several fish samples, In addition, we wish to thank Argonne's Center for Educational Affairs for supporting S. E. Groves under the Undergraduate Research Participation Program. (a) 6l24 ye? + 1l] 3,240.9 19 >8 <13.0 106 +8 204 + 8 12,9+1,9 27 9.7 +2,4 260 + 10 Tissue 239, 240.4 298/239 ' 240, 238, u 238, /233 ' 240, Shell 239,240), 238, Sample 239,2 Distribution of 2385 and 39 4054 (FCi/g dry wt) (2! between shell and tissue of crayfish as a function of individual length, Table 5. increase in 238py activity, apparently independent of their feeding be- havior, 527