COLLABORATING EDITORS 



Austin M. Brues, Director, Division of Biological and Medical Research, 



Argonne National Laboratory, Lemont, Illinois 

 Berwind p. Kaufmann, Resident Investigator, Carnegie Institution of 



Washington, Cold Spring Harbor, New York 



Hermann J. Muller, Professor of Zoology, Indiana University, Bloom- 

 ington 



Lauriston S. Taylor, Chief, Atomic and Radiation Physics Division, 

 National Bureau of Standards, Washington, D.C. 



