i PREFACE 
iv 
studies may be grouped round the concept of evo- 
lution. All the studies appeared in The New 
‘Statesman and are published in this form with the 
kind permission of the proprietors and editor. 
J. ARTHUR THOMSON. 
MarIscHAL COLLEGE, ° 
Tue University oF ABERDEEN, 
January 1919. 
