DIFFICULTIES OF THE THEORY 281 



to be injurious, it will be modified; or if it be not so 

 the being will become extinct as myriads have become 

 extinct. 



Natural selection tends only to make each organic 

 being as perfect as, or slightly more perfect than, the 

 other inhabitants of the same country with which it 

 comes into competition. I And we see that this is the, 

 standard of perfection attained under nature. The en- 

 demic productions of New Zealand, for instance, are 

 perfect one compared with another; but they are now 

 rapidly yielding before the advancing legions of plants 

 and animals introduced from Europe. Natural selection 

 will not produce absolute perfection, nor do we always 

 meet, as far as we can judge, with this high standard 

 under nature. The correction for the aberration of light 

 is said by Miiller not to be perfect even in that most 

 perfect organ, the human eye. Helmholtz, whose judg- 

 ment no one will dispute, after describing in the strong- 

 est terms the wonderful powers of the human eye, adds 

 these remarkable words: "That which we have discov- 

 ered, in the way of inexactness and imperfection in the 

 optical machine and in the image on the retina, is as 

 nothing in comparison with the incongruities which we 

 have just come across in the domain of the sensations. 

 One might say that nature has taken delight in accumu- 

 lating contradictions in order to remove all foundation 

 from the theory of a pre-existing harmony between the 

 external and internal worlds." If our reason leads us 

 to admire with enthusiasm a multitude of inimitable con- 

 trivances in nature, this same reason tells us, though we 

 may easily err on both sides, that some other contriv- 

 ances are less perfect. Can we consider the sting of the 



