PROCEEDINGS 



OF 



THE ROYAL SOCIETY. 



Series B. Vol. 90, No. B 630. 



BIOLOGICAL SCIENCES. 



JAN15I9 

 Library 



CONTENTS. 



age 



The Artificial Production of Echinoderm Larvae with Two Water- Vascular 

 Systems, and also of Larvae Devoid of a Water-Vascular System. By 

 E. W. MACBRIDE, F.R.S. (Plates 4-10) 323 



Changes of Electrical Conductivity under Geotropic Stimulation. By 



JAMES SMALL, M.Sc. (Lond.), F.L.S. 349 



PRINTED AND PUBLISHED FOR THE ROYAL SOCIETY BY 

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

 Price Four Shillings and Sixpence. 



No. B 630. 



December 20, 1918. 



