1. Medical Research Center, Brookhaven National Laboratory, Upton, N. Y., and the Department of Hematology, The Mount Sinai Hospital, New York, N. Y.
2. Present address: Toronto General Hospital, Toronto, Ont., Canada.
3. Division of Medical Physics, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
4. Department of Hematology, The Mount Sinai Hospital, New York, N. Y.
5. Karolinsk Sjukhuset, Stockholm, Sweden. At present:
6. Division of Experimental Pathology, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.