siiiiiiiiiiiiiiiiiiiiisi»iiin»aiiuii:!UMifimi M iii£Wiiriiiumnffh§iBiiia>nu£^f]2^ 
S3 
I 
VOLUME 4 JUNE, 1918 NUMBER 6 
PROCEEDINGS 
OF THE 
National Academy 
of Sciences 
OF THE 
UNITED STATES OF AMERICA 
EDITORIAL BOARD 
Raymond Pearl, Chairman Edwin B. Wilson, Managing Editor 
Arthur L. Day, Home Secretary George E. Hale, Foreign Secretary 
J. J. Abel J. P. Iddings E. H. Moore 
J. M. Clarke Jacques Loeb A. A. Noyes 
H. H. Donaldson Graham Lusk Alexander Smith 
E. B. Frost A. G. Mayer E. L. Thorndike 
R. A. Harper R. A. Millikan W. M. Wheeler 
Publication Office: Williams & Wilkins Company, Baltimore 
Editorial Office: Massachusetts Institute of Technology, Cambridge 
Home Office of the Academy: Washington, D. C. 
1 
