106 EVOLUTION AND NATURAL THEOLOGY. 



renders it more liable to be acted upon by 

 Natural Selection ; for the preponderance 

 of wingless beetles in Madeira is far too re- 

 markable to be due to any accidental cause. 

 Darwin has pointed out that it would be an 

 advantage to birds or insects landing on oceanic 

 islands to have their powers of flight eithe: 

 increased or diminished, for such islands are 

 generally of small extent, and liable to be swept 

 by hurricanes, and therefore their winged 

 inhabitants are particularly liable to be blown 

 out to sea. If their powers of flight were 

 increased, they would stand a better chance 

 either of returning to the shore they had left, 

 or of reaching some other land ; but if their 

 flight was too weak to give them a reasonable 

 chance of ever reaching land again, when they 

 were once blown away from shore, it would 

 obviously be an advantage to them to become 

 more and more terrestrial in their habits, or 

 even ultimately to lose the power of flight 

 altogether, as they would not then be exposed 

 to the danger of being blown out to sea, and 

 drowned.* 



* " Origin of Species," pp. 153, 154. 



