H 



PHILOSOPHICAL 



TRANSACTIONS 



OF THE 



ROYAL SOCIETY OF LONDON. 



SERIES A. 



CONTAINING PAPERS OF A BIOLOGICAL CHARACTER. 



VOL. 220. 



>*^ 

 'V^' 



PRINTED AND PUBLISHED FOR THE KOYAL SOCIETY BY 

 HARRISON AND SONS, 44-47, ST. MARTIN'S LANE, LONDON, W.C. 2, 



printers in r&inarj to fits Pajwtg. 



JUNE, 1920. 



