PREFACE 



^T^HE right of any book to live must be deteiTnincd finally 

 ^ by what is on its pages. Nevertheless, when the author 

 of a scientific book undertakes such a task as I have under- 

 taken in this one, his natural and acquired fitness for carry- 

 ing out his project ought to count in some measure toward 

 the determination. An attempt to speak with some degree 

 of originality and authority on subjects so remote from one 

 another as are the chemistry of organisms, heredity, human 

 consciousness, and the nature of knowledge, would be some- 

 what audacious even if made by an author of secure reputa- 

 tion as an investigator in one or more of these fields. When, 

 however, the attempt is that of a complete stranger to all 

 the fields, as thus judged, the attempt is no longer entitled 

 to be called "somewhat audacious." It is audacious out and 

 out, and if defensible at all is defensible in spite of its 

 audacity. But the very nature of the task I have attempted 

 seems to require me to contend that while it is audacious it 

 is yet not impossible, and to point out something of my own 

 qualifications for performing it. 



Such professional fitness as I have rests primarily on my 

 being a general zoologist in the proper sense ; that is, a 

 student of the phenomena of the animal world without ex- 

 clusion of any aspect of that world from professional in- 

 terest and some measure of professional attention. Tliese 

 facts of my vocation, and of my conception of the nature of 

 that vocation are crucial for the quality not only of tliis 

 book but all my general writings. 



If once one becomes as deeply convinced as I am of botli 

 the fundamental unity and the fundamental diversity of all 



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