404 Recapitulation. Chap. xv. 



CHAPTEK 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 extended — 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 re- 

 capitulated. 



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 wnth, human reason, 

 but by the accumulation of innumerable slight variations, each good 

 for the individual possessor. Nevertheless, this difficulty, though 

 appearing to our imagination insuperably great, cannot be con- 

 sidered 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 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 natural selection ; and one of the most curious of these 



