6 INTRODUCTORY [ch. 



followers of Darwin, this generally means an inter- 

 pretation in terms of natural selection. Granted this 

 factor it remains to shew that the character in question 

 confers some advantage upon the individuals that 

 possess it. For unless it has a utilitarian value of some 

 sort it clearly cannot have arisen through the operation 

 of natural selection. However when it comes to the 

 point direct proof of this sort is generalfy difficult to 

 obtain. Consequently the work of most students of 

 adaptation consists in a description of the character 

 or characters studied together with such details of 

 its life-history as may seem to bear upon the point, 

 and a suggestion as to how the particular character 

 studied may be of value to its possessors in the struggle 

 for existence. In this way a great body of most 

 curious and interesting facts has been placed on 

 record, and many ingenious suggestions have been 

 made as to the possible use of this or that character. 

 But the majority of workers have taken natural 

 selection for granted and then interested themselves 

 in shewing how the characters studied by them might 

 be of use. Probably there is no structure or habit 

 for which it is impossible to devise some use 1 , and 

 the pursuit has doubtless provided many of its devotees 

 with a pleasurable and often fascinating exercise of 

 the imagination. So it has come about that the facts 



1 Ray gives the case of an elephant "that was observed always 

 when he slept to keep his trunk so close to the ground, that nothing 

 but Air could get in between them," and explains it as an adaptation 

 in habit to prevent the mice from crawling into its lungs — "a strange 

 sagacity and Providence in this Animal, or else an admirable instinct." 



