430 CONCLUDING REMARKS. Chap. XXVIII. 



distinct genera and orders within the same great cla 



for instance, whales, mice, birds, and fishes — are all the descen 



ants of 



pro 



Imit that 



whole vast amount of difference between these forms of life has 

 primarily arisen from simple variability. To consider the sub- 

 ject under this point of view is enough to strike one dumb 

 with amazement. But our amazement ought to be lessened 

 when we reflect that beings, almost infinite in number, during 

 an almost infinite lapse of time, have often had their whole 

 organisation rendered in some degree plastic, and that each 



slight modification of structure which was in any way benefi 



a 



cial under excessively complex conditions of life, will ha^v 

 been preserved, whilst each which was in any way injurioi 

 will have been rigorously destroyed. And the long-continued 

 accumulation of beneficial variations will infallibly lead to 

 structures as diversified, as beautifully adapted for various 

 purposes, and as excellently co-ordinated, as we see in the 

 animals and plants all around us. Hence I have spoken of 

 selection as the paramount power, whether applied by man to 

 the formation of domestic breeds, or by nature to the produc- 

 tion of species. I may recur to the metaphor given in a former 

 chapter : if an architect were to rear a noble and commodious 

 edifice, without the use of cut stone, by selecting from the 

 fragments at the base of a precipice wedge-formed stones 

 for his arches, elongated stones for his lintels, and flat stones for 



his roof, we should admire his skill and regard him as the 



paramount power. Now, the fragments of stone, though indis- 

 pensable to the architect, bear to the edifice built by him the 



elation which the fluctuating variations of each 



6 



being bear to the varied and admirable structures ultimately 

 acquired by its modified descendants. 





Some authors have declared that natural selection explains 

 nothing, unless the precise cause of each slight individual dif- 

 ference be made clear. Now, if it were explained to a savage 

 utterly ignorant of the art of building, how the edifice had been 

 raised stone upon stone, and why wedge-formed fragments were 

 used for the arches, flat stones for the roof, &c. ; and if the use 

 of each part and of the whole building were pointed out, it 

 would be unreasonable if he declared that nothing had been 





I 



