xii INTRODUCTION 



and the social perspective, witli its conscious 

 application to evolutionary research, has been 

 little employed by naturalists since Darwin 

 and Wallace, despite its extraordinary 

 fruitfulness in their hands. Now, however, 

 it begins to return, witness the Eugenic 

 movement: and in these pages we shall not 

 hesitate to avail ourselves of it. 



We may even utilize it for teaching pur- 

 poses, beginning with the doctrine of natural 

 selection. As Paley's famous "watch argu- 

 ment" appeared at the outset of the me- 

 chanical age, so again at its culmination 

 we may avail ourselves of the conspicuous 

 progress of invention to explain and illustrate 

 Darwin's great doctrine. In fact, we may 

 socratically elicit it from the freshman who 

 supposes himself quite unacquainted with 

 biology or its theories. For he knows the 

 points of a bicycle, and something of the } 

 story of its development from his father's 

 "bone-shaker," at one time by the introduc- 

 i %^ tion of ball-bearings, at another by the inven- 

 tion of pneumatic tyres, each new make, 

 thanks to this or that better "adaptation," 

 being eminently successful in surviving? 

 against its kindred but less developed com-\ 

 petitors in the struggle for existence. From 

 bicycle, or similarly motor or aeroplane, we 

 pass readily enough to bicyclist, to racehorse 



