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ication of one part will often have entailed on other parts diversified changes of no direct use。 So again characters which formerly were useful； or which formerly had arisen from correlation of growth； or from other unknown cause； may reappear from the law of reversion； though now of no direct use。 The effects of sexual selection； when displayed in beauty to charm the females； can be called useful only in rather a forced sense。 But by far the most important consideration is that the chief part of the organisation of every being is simply due to inheritance； and consequently； though each being assuredly is well fitted for its place in nature； many structures now have no direct relation to the habits of life of each species。 Thus； we can hardly believe that the webbed feet of the upland goose or of the frigate…bird are of special use to these birds； we cannot believe that the same bones in the arm of the monkey； in the fore leg of the horse； in the wing of the bat； and in the flipper of the seal； are of special use to these animals。 We may safely attribute these structures to inheritance。 But to the progenitor of the upland goose and of the frigate…bird； webbed feet no doubt were as useful as they now are to the most aquatic of existing birds。 So we may believe that the progenitor of the seal had not a flipper； but a foot with five toes fitted for walking or grasping； and we may further venture to believe that the several bones in the limbs of the monkey； horse； and bat； which have been inherited from a common progenitor； were formerly of more special use to that progenitor； or its progenitors； than they now are to these animals having such widely diversified habits。 Therefore we may infer that these several bones might have been acquired through natural selection； subjected formerly； as now； to the several laws of inheritance； reversion； correlation of growth； &c。 Hence every detail of structure in every living creature （making some little allowance for the direct action of physical conditions） may be viewed； either as having been of special use to some ancestral form； or as being now of special use to the descendants of this form either directly； or indirectly through the complex laws of growth。
Natural selection cannot possibly produce any modification in any one species exclusively for the good of another species； though throughout nature one species incessantly takes advantage of； and profits by； the structure of another。 But natural selection can and does often produce structures for the direct injury of other species； 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 this snake is furnished with a rattle for its own injury； namely； to warn its prey to escape。 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。 But I have not space here to enter on this and other such cases。
Natural selection will never produce in a being anything injurious to itself； 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 comes 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 has to struggle for existence。 And we see that this is the degree 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 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； on high authority； not to be perfect even in that most perfect organ； the eye。 If our reason leads us to admire with enthusiasm a multitude of inimitable contrivances in nature； this same reason tells us； though we may easily err on both sides； that some other contrivances are less perfect。 Can we consider the sting of the wasp or of the bee as perfect； which； when used against many attacking animals； cannot be withdrawn； owing to the backward serratures； and so inevitably causes the death of the insect by tearing out its viscera？
If we look at the sting of the bee； as having originally existed in a remote progenitor as a boring and serrated instrument； like that in so many members of the same great order； and which has been modified but not perfected for its present purpose； with the poison originally adapted to cause galls subsequently intensified； we can perhaps understand how it is that the use of the sting should so often cause the insect's own death： for if on the whole the power of stinging be useful to the community； it will fulfil all the requirements of natural selection； though it may cause the death of some few members。 If we admire the truly wonderful power of scent by which the males of many insects find their females； can we admire the production for this single purpose of thousands of drones； which are utterly useless to the community for any other end； and which are ultimately slaughtered by their industrious and sterile sisters？ It may be difficult； but we ought to admire the savage instinctive hatred of the queen…bee； which urges her instantly to destroy the young queens her daughters as soon as born； or to perish herself in the combat； for undoubtedly this is for the good of the community； and maternal love or maternal hatred； though the latter fortunately is most rare； is all the same to the inexorable principle of natural selection。 If we admire the several ingenious contrivances； by which the flowers of the orchis and of many other plants are fertilised through insect agency； can we consider as equally perfect the elaboration by our fir…trees of dense clouds of pollen； in order that a few granules may be wafted by a chance breeze on to the ovules？
Summary of Chapter。 We have in this chapter discussed some of the difficulties and objections which may be urged against my theory。 Many of them are very grave； but I think that in the discussion light has been thrown on several facts； which on the theory of independent acts of cr