254 UTILITARIAN DOCTRINE, HOW FAR TRUE: 



it coiild be proved that any part of the structure of any 

 one species had been formed for the exclusive good of 

 another species, it would annihilate my theory, for such 

 could not have been produced 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 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 whilst 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 endeavour 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 conditions of life, if any part 



