PREFACE 



THE subject, with which the following pages deal, formed 

 the material for certain Arris and Gale Lectures, de- 

 livered in the Theatre of the Royal College of Surgeons 

 of England during the years 1915 and 1916. Chapter XXI. 

 consists of a condensed, and only partial, account of the 

 subject treated in one such Lecture on " The Influence 

 of the Arboreal Habit in the Evolution of the Reproduc- 

 tive System," delivered on March 22nd, 1915; and the 

 remaining chapters formed the basis of three Lectures 

 on " The Influence of the Arboreal Habit in the Evolu- 

 tion of Man," delivered on February 28th, March 1st, 

 and March 3rd, 1916. 



Among their literary defects are those which are in- 

 separable from their origin, since they are at best but 

 elaborated notes of separated headings under which the 

 Lectures were originally planned. The gift, which was 

 so peculiarly conspicuous a possession of Huxley, of 

 endowing the written page with the interest felt by the 

 lecturer in the preparation of his subject, is a rare one. 

 For the most part, the written notes of lectures are wont 

 to present themselves as mere disconnected assertions, 

 woven around a series of apparently disjointed central 

 ideas. It is this inherent difficulty of reducing the under- 

 lying thought, and the spoken word to a consecutive 

 written statement, that is appealed to as an excuse for 

 the partially woven condition in which the material is 

 presented to the reader. And this excuse is urged the 

 more insistently since an alternative one will readily 

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