BIOMETRIKA 
A JOURNAL FOR THE STATISTICAL STUDY OF 
BIOLOGICAL PROBLEMS 
FOUNDED BY 
W. F. R. WELDON, FRANCIS GALTON and KARL PEARSON 
EDITED BY 
KARL PEARSON 
VOLUME XIII 
October 1920 to October 192] 
CAMBRIDGE 
AT THE UNIVERSITY PRESS 
LONDON: FETTER LANE, E.G. 4 
(C. F. CLAY, Manageb) 
AND H. K. LEWIS AND CO., Ltd., 136, GOWER STREET, W.C. 1 
WHELDON AND WESLEY, Ltd., 28, ESSEX STREET, STRAND, W.C. 2 
CHICAOO : UNlVEliSITY (ll' CHICAGO PRESS 
(agents foe THE UNITED STATES AND CANADA) 
BOJin.\y, CALCUTTA AND MADRAS : MACMILLAN AND CO., LIMITED 
TOKYO: THE jrARDZKN-KAnUSHIKI-KAISHA 
\.\U rit/Jils rexervcd] 
