PREFACE 



The essays on evolution included in this book have 

 not been placed in the order of their original publication, 

 but are grouped according to the relationship of the 

 subjects with which they deal. The first is concerned 

 with the time in which evolution took place, and is a reply 

 to the late Lord Salisbury's contention that the age of the 

 habitable globe is not sufficient for the process as con- 

 ceived by Darwin and Wallace. The second attempts 

 to define the material which has been subject to organic 

 evolution — species. The third contrasts the Darwin- 

 Wallace with the Lamarck-Spencer theory of evolution. 

 Heredity, the arbiter between the two rival theories, 

 forms the subject of the fourth and fifth essays. The 

 sixth deals with a neglected episode in the history of 

 modern views on heredity and evolution, and shows how 

 they were born out of due time but afterwards died in 

 the mind of James Cowles Prichard, the great anthropo- 

 logist. The seventh, discussing Huxley's attitude 

 towards Natural Selection, maintains that above all it is 

 the experience of the student of living nature which 

 inspires confidence in the theory. The eighth and ninth 

 essays form the natural continuation of the argument of 

 the seventh, and show that the immense number of facts 

 grouped under Mimicry are consistent with an interpreta- 

 tion based on Natural Selection, and inconsistent with 

 other attempted explanations. The argument of the 



