166 THE ORIGIN OF SPECIES 



namely, to warn its prey. I would almost as soon believe that the 

 cat curls the end of its tail when preparing to spring, in order to 

 warn the doomed mouse. It is a much more probable view that the 

 rattlesnake uses its rattle, the cobra expands its frill and the puff- 

 adder swells while hissing so loudly and harshly, in order to alarm 

 the many birds and beasts which are known to attack even the 

 most venomous species. Snakes act on the same principle which 

 makes the hen ruffle her feathers and expand her wings when a dog 

 approaches her chickens. But I have not space here to enlarge on 

 the many ways by which animals endeavor to frighten away their 

 enemies. 



Natural selection will never produce in a being any structure 

 more injurious than beneficial to that being, for natural selection 

 acts solely by and for the good of each. No organ will be formed, 

 as Paley has remarked, for the purpose of causing pain or for 

 doing an injury to its possessor. If a fair balance be struck between 

 the good and evil caused by each part, each will be found on the 

 whole advantageous. After the lapse of time, under changing con- 

 ditions of life, if any part comes to be injurious, it will be modi- 

 fied; 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-per- 

 fect as, or slightly more perfect than, the other inhabitants of the 

 same country with which it comes into competition. And we see 

 that this is die standard of perfection attained under nature. The 

 endemic 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 perfec- 

 tion, 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 Muller not to be perfect even in that most perfect organ, 

 the human eye. Helmholtz, whose judgment no one will dispute, 

 after describing in the strongest terms the wonderful powers of 

 the human eye, adds these remarkable words: "That which we have 

 discovered in the way of inexactness and imperfection in the op- 

 tical machine and in the image on the retina, is as nothing in com- 

 parison with the incongruities which we have just come across in 

 the domain of the sensations. One might say that nature has taken 

 delight in accumulating contradictions in order to remove all foun- 

 dation from the theory of a pre-existing harmony between the ex- 

 ternal and internal worlds." If our reason leads us to admire with 

 enthusiasm a multitude of inimitable contrivances in nature, this 



