LIBRARY 



UNIVERSITY OF CALIFORNIA 

 SANTA BARBARA 



PREFACE. 



MUCH misunderstanding exists, even in the minds 

 of educated people, concerning the relation of the 

 thinking world to the theory of evolution. Com- 

 paratively few, except those who have made special 

 study of the subject, are aware even of the sort of 

 arguments which have led scientists to accept evo- 

 lution. The question is, however, too important for 

 any educated person to be satisfied with ignorance. 

 The excuse for the present book is to fill a vacancy 

 in our literature : to give for those who are inter- 

 ested in the vital questions of the age a brief account 

 of this theory as it stands to-day in the minds of 

 scientists. Much advance has been made since the 

 time of Darwin's first writings. Some of his claims 

 have been substantiated and some disproved. His 

 own theory has been examined, tested, and partially 

 abandoned, and others have been advanced in its 

 place. This book is intended to indicate as nearly 

 as possible the foundation which the theory has 

 built for itself. I shall therefore attempt to sum- 

 marize the various lines of arguments advanced and 

 discussed upon all sides ; to enumerate the import- 

 ant difficulties which have arisen, together with the 



