PREFACE. 



THE present volume consists of essays which I have 

 contributed to various periodicals, or read before scien- 

 tific societies during the last fifteen years, with others 

 now printed for the first time. The two first of the- 

 series are printed without alteration, because, having 

 gained me the reputation of being an independent 

 originator of the theory of " natural selection," they 

 may be considered to have some historical value. I 

 have added to them one or two very short explanatory 

 notes, and have given headings to subjects, to make 

 them uniform with the rest of the book. The other 

 essays have been carefully corrected, often consider- 

 ably enlarged, and in some cases almost rewritten, se- 

 as to express more fully and more clearly the views 

 which I hold at the present time ; and as most of 

 them originally appeared in publications which have- 

 a very limited circulation, I believe that the larger 

 portion of this volume will be new to many of my 

 friends and to most of my readers. 



I now wish to say a few words on the reasons which 

 have led me to publish this work. The second essay, 

 especially when taken in connection with the first, 

 contains an outline sketch of the theory of the origin 

 of species (by means of what was afterwards termed 

 by Mr. Darwin "natural selection,") as conceived 



