PEEFACE 



THE present volume consists mainly of a reprint of two 

 volumes of essays Contributions to the Theory of Natural 

 Selection, which appeared in 1870, with a second edition in 

 1871, and has now been many years out of print; and, 

 Tropical Nature and Other Essays, which appeared in 1878. 



In preparing a new edition of these works to appear as 

 a single volume I have thought it advisable to omit two 

 essays that on "The Malayan Papilionidae " as being too 

 technical for general readers, and that on " The Distribution 

 of Animals as indicating Geographical Changes," which con- 

 tains nothing that is not more fully treated in my other 

 works. Another essay "By - Paths in the Domain of 

 Biology" has also been partly omitted, one portion of it 

 forming a short chapter on " The Antiquity and Origin of 

 Man," while another portion has been incorporated in the 

 chapter on " The Colours of Animals and Sexual Selection." 

 More than compensating for these omissions are two new 

 chapters " The Antiquity of Man in North America " and 

 "The Debt of Science to Darwin." 



Many corrections and some important additions have been 

 made to the text, the chief of which are indicated in the 

 table given below ; and to facilitate reference the two original 

 works have separate headings, and form Parts I. and II. of 

 the present volume. 



