NATURAL SELECTION 



And there are other special classes of pheno- 

 mena to which it has been applied with equally 

 remarkable success. But when a theory, de- 

 duced from the observed general facts of or- 

 ganic life, and invoking no agencies but such 

 as are known to be in operation, is found on 

 trial to account for such an enormous mass of 

 special facts, for which no other valid explana- 

 tion has been propounded, — we may well say 

 of it, as Laplace said of his own Nebular Hy- 

 pothesis, that the chances in favour of its being 

 a true explanation are many thousand million 

 to one. 



45 



