374 EVOLUTION, OLD AND NEW. 



some purpose, and do not like having that purpose 

 interfered with by something which can carry them all- 

 whithers, whether they like it or no. If they are flying 

 and find the wind taking them in a wrong direction, or 

 seaward which they know will be fatal to them 

 they stop flying as soon as may be, and alight on terra, 

 firma. But if the wind is very prevalent the beetles 

 can find but little opportunity for flying at all : they 

 will therefore lie quiet all day and do as best they can 

 to get their living on foot instead of on the wing. 

 There will thus be a long-continued disuse of wings, 

 and this will gradually diminish the development of 

 the wings themselves, till after a sufficient number of 

 generations these will either disappear altogether, or 

 be seen in a rudimentary condition only. For each 

 beetle which has made but little use of its wings will be 

 liable to leave offspring with a slightly diminished wing, 

 some other organ which has been used instead of the wing 

 becoming proportionately developed. It is thus seen 

 that the conditions of existence are the indirect cause 

 of the wings becoming rudimentary, inasmuch as they 

 preclude the beetles from using them ; the disuse 

 however on the part of the beetles themselves is the 

 direct cause. 



Now let us see how Mr. Darwin deals with the same 

 case. He writes : 



" In some cases we might easily set down to disuse, 

 modifications of structure which are wholly or mainly 

 due to natural selection." Then follow the facts about 

 the beetles of Madeira, as I have given them above. 

 While we are reading them we naturally make up our 



