BJEA UTT, HOW ACQ UIRED. 193 



through natural selection. Although many statements 

 may be found in works on natural history to this effect, I 

 cannot find even one which seems to me of any weight. It 

 is admitted that the rattlesnake has a poison fang for its 

 own defence and for the destruction of its prey; but some 

 authors suppose that at the same time it is furnished with 

 a rattle for its own injury, namely, to warn its prey. I 

 would almost as soon beheve 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 pufE-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 pos- 

 sessor. 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 

 conditions of life, if any part comes to be injurious, it will 

 be modified; or if it be not so, the being will become ex- 

 tinct as myriads have become extinct. 



Natural selection tends only to make each organic being 

 as perfect as, or slightly more perfect than the other in- 

 habitants of the same country with which it comes into com- 

 petition. And we see that this is the standard of perfec- 

 tion 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 ad- 

 vancing legions of plants and animals introduced from 

 Europe. Natural selection will not produce absolute per- 

 fection, 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 ]M tiller not to be perfect 



