72 NATURAL SELECTION. 



order that new and unoccupied places should be left for 

 naftiral selection to fill up by improving some of the vary- 

 ingunhabitants. For as all the inhabitants of each country 

 are struggling together with nicely balanced forces, ex- 

 tremely slight modifications in the structure or habits of 

 one species would often give it an advantage over others ; 

 and still further modifications of the same kind would often 

 still further increase the advantage, as long as the species 

 continued under the same conditions of life and profited by 

 similar means of subsistence and defence. No country can 

 be named in which all the native inhabitants are now so 

 perfectly adapted to each other and to the physical condi- 

 tions under which they live, that none of them could be 

 still better adapted or improved ; for in all countries the 

 natives have been so far conquered by naturalized produc- 

 tions that they have allowed some foreigners to take firm 

 possession of the land. And as foreigners have thus in 

 every country beaten some of the natives, we may safely 

 conclude that the natives might have been modified with 

 advantage, so as to have better resisted the intruders. 



As man can produce, and certainly has produced, a great 

 result by his methodical and unconscious means of selection, 

 what may not natural selection effect ? Man can act only 

 on external and visible characters ; Nature, if I may be 

 allowed to personify the natural preservation or survival of 

 the fittest, cares nothing for appearances, except in so far 

 as they are useful to any being. She can act on every 

 internal organ, on every shade of constitutional difference, 

 on the whole machinery of life. Man selects only for his 

 own good ; Nature, only for that of the being which she 

 tends. Every selected character is fully exercised by her, 

 as is implied by the fact of their selection. Man keeps the 

 natives of many climates in the same country. He seldom 

 exercises each selected character in some peculiar and fitting 

 manner ; he feeds a long and a short-beaked pigeon on the 

 same food; he does not exercise a long-backed or long- 

 legged quadruped in any peculiar manner ; he exposes 

 sheep with long and short wool to the same climate ; does 

 not allow the most vigorous males to struggle for t&m 

 females; he does not rigidly destroy all inferior animals, 

 but protects during each varying season, as far as lies in his 

 power, all his productions. He often begins his selection 

 by some half-monstrous form, or at least by some modifica- 

 tion prominent enough to catch the eye or to be plainly 



