PREFACE 



THE kindly reception accorded to " A History of 

 Birds " ; — the second in the order of final sequence 

 of this series — encourages me to believe that 

 these volumes on vertebrate animal life which I pro- 

 jected really supplied a need felt by that increasing body 

 of men and women who profess themselves "nature 

 lovers". 



Having conceived the plan of recording, at any rate 

 in broad outline, the history of the vertebrates from the 

 evolutionist's point of view, I allotted to myself, as many 

 already know, the task of writing the volume on Birds, 

 and proposed to edit the remaining volumes rather than 

 attempt to write them. And this because the day is 

 now past when any single writer can hope to achieve 

 such a task with even tolerable success, for this is the 

 day of specialists. As a consequence, for the first time 

 in the annals of natural history, the complete life-story 

 of the reptiles, amphibia, and fishes, and those primitive 

 creatures which lie at the foundations, so to speak, of the 

 great house of the vertebrates, is told as only specialists 

 can tell it. The very existence of these primitive ani- 

 mals is unsuspected by most of us, but, as Professor 

 Arthur Thomson shows, they present us with some most 

 interesting and most important problems. The student 

 of sociology will find in his chapters, no less than in 

 those concerning more familiar creatures, much food 

 for reflection bearing on the subjects of adaptation to 

 environment, degeneration, and so on. 



