xin.] CRITICISMS ON " THE ORIGIN OF SPECIES:' 317 



with as much precision as if man had "' consciously 



selected " it by the aid of a sieve. Physical Geology is 

 full of such selections — of the picking out of the soft 

 from the hard, of the soluble from the insoluble, of the 

 fusible from the infusible, by natural agencies to which 

 we are certainly not in the habit of ascribing con- 

 sciousness. 



But that which wind and sea are to a sandy beach, 

 the sum of influences, which we term the " conditions 

 of existence," is to living organisms. The weak are 

 sifted out from the strong. A frosty night " selects " 

 the hardy plants in a plantation from among the tender 

 ones as effectually as if it were the wind, and they, the 

 sand and pebbles, of our illustration ; or, on the other 

 hand, as if the intelligence of a gardener had been 

 operative in cutting the weaker organisms down. The 

 thistle, which has spread over the Pampas, to the 

 destruction of native plants, has been more effectually 

 "selected" by the unconscious operation of natural con- 

 ditions than if a thousand agriculturists had spent their 

 time in sowing it. 



It is one of Mr. Darwin's many great services to 

 Biological science that he has demonstrated the sis:- 

 nificance of these facts. He has shown that — given 

 variation and given change of conditions — the inevitable 

 result is the exercise of such an influence upon organisms 

 that one is helped and another is impeded ; one tends 

 to predominate, another to disappear ; and thus the 

 living world bears within itself, and is surrounded by, 

 impulses towards incessant change. 



But the truths just stated are as certain as any other 

 physical laws, quite independently of the truth, or false- 

 hood, of the hypothesis which Mr. Darwin has based 

 upon them ; and that M. Flourens, missing the substance 

 and grasping at a shadow should be blind to the admi- 



