CHAPTER XV 

 Recapitulation and Conclusion 



Recapitulation of the objections to the theory of Natural Selection — 

 Recapitulation of the general and special circumstances in its 

 favour — Causes of the general belief in the immutability of 

 species — How far the theory of Natural Selection may be ex- 

 tended — Effects of its adoption on the study of Natural History 

 — ^Concluding remarks. 



AS this whole volume is one long argument, it may be 

 convenient to the reader to have the leading facts 

 - and inferences briefly recapitulated. 



That many and serious objections may be advanced against 

 the theory of descent with modification through variation 

 and natural selection, I do not deny. I have endeavoured to 

 give to them their full force. Nothing at first can appear 

 more difficult to believe than that the more complex organs 

 and instincts have been perfected, not by means superior to, 

 though analogous with, human reason, but by the accumu- 

 lation of innumerable slight variations, each good for the 

 individual possessor. Nevertheless, this difficulty, though 

 appearing to our imagination insuperably great, cannot be 

 considered real if we admit the following propositions, 

 namely, that all parts of the organisation and instincts offer, 

 at least, individual differences — that there is a struggle for 

 existence leading to. the preservation of profitable deviations 

 of structure or instinct — and, lastly, that gradations in the 

 state of perfection of each organ may have existed, each good 

 of its kind. The truth of these propositions cannot, I think, 

 be disputed. 



It is, no doubt, extremely difficult even to conjecture by 

 what gradations many structures have been perfected, more 

 especially amongst broken and failing groups of organic 

 beings, which have suffered much extinction ; but we see so 

 many strange gradations in nature, that we ought to be ex- 



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