Organs of little apparent Importance, as affected by 



Natural Selection. 



* 



As natural selection acts by life and death, — by the 

 survival of the fittest, and by the destruction of the 

 less well-fitted individuals, — I have sometimes felt 

 great difficulty in understanding the origin or forma- 

 tion of parts of little importance; almost as great, 

 though of a very different kind, as in the case of the 

 most perfect and complex organs. 



In the first place, we are much too ignorant in regard 

 to the whole economy of any one organic being, to say 

 what slight modifications would be of importance or 

 not. In a former chapter I have given instances of 

 very trifling characters, such as the down on fruit and 

 the colour of its flesh, the colour of the skin and hair of 

 quadrupeds, which, from being correlated with consti- 

 tutional differences or from determining the attacks 

 of insects, might assuredly be acted on by natural 

 selection. The tail of the giraffe looks like an 

 artificially constructed fly-flapper; and it seems at 

 first incredible that this could have been adapted for 

 its present purpose by successive slight modifications, 

 each better and better fitted, for so trifling an object as 

 to drive away flies ; yet we should pause before being 

 too positive even in this case, for we know that the 

 distribution and existence of cattle and other animals 

 in South America absolutely depend on their power of 

 resisting the attacks of insects : so that individuals 

 which could by any means defend themselves from 

 these small enemies, would be able to range into new 

 pastures and thus gain a great advantage. It is not 

 that the larger quadrupeds are actually destroyed 



