476 REOAPITULATION. 



OHAPTBE XV. 



EECAPITULATION AND CONCLUSIOK. 



Recapitulation of tlae objections to the tlieorj 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 — 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 en- 

 deavored to give to them their full force. Nothing at first 

 can appear more diflicult 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 accumulation of innumerable slight variations, 

 each good for the individual possessor. Nevertheless, this 

 difficulty, though appearing to our imagination insuper- 

 ably great, can not be considered real if we admit the fol- 

 lowing propositions, namely, that all parts of the organi- 

 zation and instincts ofEer, at least, individual difEerences — 

 that there is a struggle for existence leading to the preser- 

 vation of profitable deviations of structure or instinct — 

 and, lastly, that gradations in the state of pei-fection 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 sufEered much extinction; but 

 we see so many strange gradations in nature, that we ought 



