RECAPITULATION. 447 



CHAPTER XV. 



RECAPITULATION AND CONCLUSION. 



Recapitulation of the Objections to the Theory of Natural Selection — 

 Recapitulation of the General and Special Circumstances in its 

 Favor — Causes of the General Belief in the Immutability of Species 

 — How far the Theory of Natural Selection may be extended — 

 Effects of its Adoption on the Study of Natural History — Con- 

 cluding 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 endeavored 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 accumula- 

 tion 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 organization and instincts offer, 

 at least, individual differences — that there is a struggle 

 for existence leading to the preservation of profitable devia- 

 tions 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 can- 

 not, I think, be disputed. 



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

 what gradations many structures have been perfected, more 

 especially among 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 

 extremely cautious in saying that any organ or instinct, or 

 any whole structure, could not have arrived at its present 

 state by many graduated steps. There are, it must be 

 admitted* cases of special difficulty opposed to the theory of 



