ORGANS OP LITTLE APPAEENT IMPORTANCE. 245 



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 formation 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 se- 

 lection. The tail of the giraffe looks like an artifi- 

 cially constructed fly-flapper; and it seems at first in- 

 credible that this could have been adapted for its present 

 purpose by successive slight modifications, each better 

 and better fitted, for so trifiing an object as to drive 

 away flies; yet we should pause before being too posi- 

 tive 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 ene- 

 mies, would be able to range into new pastures and 

 thus gain a great advantage. It is not that the larger 

 quadrupeds are actually destroyed (except in some rare 



