162 UTILITARIAN DOCTRINE HOW FAR TRUE ■ [Chap. VI. 



kingdom. When the female is as beautifully coloured as the male, 

 which is not rarely the case with birds and butterflies, the cause 

 apparently lies in the colours acquired through sexual selection 

 having been transmitted to both sexes, instead of to the males 

 alone. How the sense of beauty in its simplest form — that is, the 

 reception of a peculiar kind of pleasure from certain colours, forms , 

 and sounds — was first developed in the mind of man and of the lower 

 animals, is a very obscure subject. The same sort of difficulty is 

 presented, if we enquire how it is that certain flavours and odours 

 give pleasure, and others displeasure. Habit in all these cases 

 appears to have come to a certain extent into ptay ; but there must 

 be some fundamental cause in the constitution of the nervous 

 system in each species. 



Natural selection cannot possibly produce any modification id 

 a species exclusively for the good of another species ; though 

 throughout nature one species incessantly takes advantage of, and 

 profits by, the structures of others. But natural selection can 

 and does often produce structures for the direct injury of other 

 animals, as we see in the fang of the adder, and in the ovipositor 

 of the ichneumon, by which its eggs are deposited in the living 

 bodies of other insects. If it could 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 iniurious tbarv beneficial to that being, for natural selection 



