preface 



IN this book I attempt to find a solution of some of the 

 most difficult of the problems of evolution. First I try to 

 show that Lamarck's explanation of evolution will not bear 

 investigation. But if the dovetailing of species into their 

 environment has not been brought about, as he maintained 

 that it had, by the moulding influence of the environment 

 itself and the development of the organism by exercise, 

 how have adaptations been effected? To account for 

 them, the Neo-Darwinian, the follower of Weismann, 

 has at his service only variations he assumes that a 

 tendency to vary pervades the whole organic world and, 

 as a regulating principle, Natural Selection. Nothing 

 further, as I hope to make clear, is wanted to account 

 for all the niceties of adaptation. Moreover, evolution 

 appears to follow certain lines, and species group them- 

 selves in orderly series. This becomes intelligible, if we 

 realise that all species, even the lowest, to a certain ex- 

 tent, pilot themselves. In other words, heredity limits 

 the range of variation, and limits it more narrowly as 

 evolution advances. 



Sexual selection and isolation present problems, which 

 though perhaps of less importance, are of the utmost 

 interest. 



The second part of the book deals with human evolution. 



