PREFATORY NOTE 



The statistical material used in these two lectures is partly drawn 

 from Dr David Heron's memoir The Influence of Unfavourable Home 

 Environment and Defective Physique on the Intelligence of School 

 Children (Galton Laboratory Memoirs, No. VIII) and from A First 

 Study of the Inheritance of Vision and of the Relative Influence of 

 Heredity and Environment on Sight by Amy Barrington and Karl 

 Pearson (Galton Laboratory Memoirs, No. V), but is also largely 

 based on hitherto unpublished material, which cannot be issued in 

 bulk until the laboratory staff has greater leisure and more ample 

 funds for publication than are at present available. 



CAMBRIDGE: PRINTED BY JOHN CLAY. M.A. AT THE UNIVERSITY PRESS 



