x PREFACE TO THE FIRST EDITION 
de Vries for the present of an excellent portrait ; and 
Mr. Francis Galton for the loan of a photograph weli 
known from earlier reproductions. The portrait of 
Mendel is reproduced from the frontispiece to Mr. 
Bateson’s ‘ Defence,’ by the permission of the Syndics 
of the Cambridge University Press. Messrs. Macmillan 
and Co. have kindly allowed the reproduction of the 
diagram which occupies p. 87, and of the table and 
figure on pp. 89 and 90. The figures facing pp. 143 
and 150 are from de Vries’ ‘ Mutationstheorie,’ pub- 
lished by Messrs. Veit. 
The attempt has been made to render the following 
pages intelligible to the general reader, as well as to 
the more scientific public, to which they are primarily 
addressed. A short glossary has been added, which 
may be found useful by those who have no previous 
acquaintance with biological terms. 
CAMBRIDGE, 
October 23, 1906. 
