PREFACE TO SECOND EDITION 



The interest of the public and the kindness 

 of the publishers have made possible a revised 

 edition of this book within a year after its first 

 publication. This has permitted the rewriting 

 of certain passages which were not well ex- 

 pressed and the introduction of considerable 

 new material which will serve, it is hoped, to 

 further elucidate some of the questions dis- 

 cussed, as well as to give results of more recent 

 work. In particular Figs. 4, 5, 9, 10, 18, 19 

 have been added and besides minor corrections 

 and additions to all the chapters considerable 

 changes have been made in Chapter III, sec- 

 tion on Maternal Inheritance, Chapter IV 

 section on Inheritance or Non-Inheritance 

 of Acquired Characters, and Chapter V sec- 

 tions on Artificial Selection, Origin of Muta- 

 tions, Past Evolution of Man, and Eugenics. 

 January, 1916 



Publisher's Note. — In the second edition, second printing, 

 August, 1917, the text was corrected by the author so as to em- 

 body some of the results of the latest investigations in this 

 subject. 



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