vi PREFACE 



one of its divisions; it was possible only to set forth 

 some of the more striking and significant facts which 

 would demonstrate the nature and meaning of that 

 department from which they were selected. The 

 illustrations were usually made concrete through the 

 use of photographs, which must naturally be lacking in 

 the present volume. In preparing the addresses for 

 publication, the verbal form of each evening's dis- 

 cussion has been somewhat changed, but there has been 

 no substantial alteration of the subjects actually dis- 

 cussed. 



The choice of materials and the mode of their pre- 

 sentations were determined by the general purpose 

 of the whole course. The audiences were made up 

 almost exclusively of mature persons of cultivated 

 minds, but who were on the whole quite unfamiliar 

 with the technical facts of natural history. It was 

 necessary to disregard most of the problematical ele- 

 ments of the doctrine so as to bring out only the basic 

 and thoroughly substantiated principles of evolution. 

 The course was, in a word, a simple message to the un- 

 scientific ; and while it may seem at first that the dis- 

 cussions of the latter chapters lead to somewhat insecure 

 positions, it should be remembered that their purpose 

 was to bring forward the proof that even the so-called 

 higher elements of human Ufe are subject to classifica- 

 tion and analysis, like the facts of the lower organic 

 world. 



It may seem that the biologist is straying beyond his 

 subject when he undertakes to extend the principles of 

 organic evolution to those possessions of mankind that 

 seem to be unique. The task was undertaken in the 



