1. Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
2. Medical Research Department, Sydney Hospital, Sydney NSW 2000 Australia, and Research Collaborator, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
3. Mount Sinai Hospital, New York, and Research Collaborator, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
4. Section of Hematology, Division of Radiation Biology, Allegheny General Hospital, Pittsburgh, Penna., and Research Collaborator, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
5. 1 Rue Heger-Bordet, Brussels, Belgium, and Research Collaborator, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.