The Origin of Species: A Variorum Text

CHAPTER XIV.

CHAPTER XIV. I:f xv. 2 RECAPITULATION AND CONCLUSION. 3 Recapitulation of the difficulties on 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 historyConcluding remarks. 3:d far the theory of Natural Selection 3:e of the objections to the theory 4 As this whole volume is one long argument, it may be convenient to the reader to have the leading facts and inferences briefly recapitulated. 5 That many and grave objections may be advanced against the theory of descent with modification through natural selection, I do not deny. 5:b and serious objections 5:e through variation and natural 6 I have endeavoured to give to them their full force. 7 Nothing at first can appear more difficult to believe than that the more complex organs and instincts should 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. 7:e instincts have 8 Nevertheless, this difficulty, though appearing to our imagination insuperably great, cannot be considered real if we admit the following propositions, namely,-that gradations in the perfection of any organ or instinct, which we may consider, either do now exist or could have existed, each good of its kind,-that all organs and instincts are, in ever so slight a degree, variable, -and, lastly, that there is a struggle for existence leading to the preservation of each profitable deviation of structure or instinct. 8:b instinct which 8:c namely, that all organs and instincts are, in ever so slight a degree , variable-that there is a struggle for existence leading to the preservation of each profitable deviation of structure or 719 instinct-and, lastly, that gradations in the perfection of every organ may have existed, each good of its kind. 8:e 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 9 The truth of these propositions cannot, I think, be disputed. 10 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; but we see so many strange gradations in nature, as is proclaimed by the canon, "Natura non facit saltum," that we ought to be extremely cautious in saying that any organ or instinct, or any whole being, could not have arrived at its present state by many graduated steps. totb nature, that we IO:C beings, which have suffered much extinction; but io:e instinct, or the whole structure, could rot] instinct, or any whole 11 There are, it must be admitted, cases of special difficulty on the theory of natural selection; and one of the most curious of these is the existence of two or three defined castes of workers or sterile females in the same community of ants; but I have attempted to show how this difficulty can be mastered. I I:C how these difficulties I t :e difficulty opposed to the theory/sterile female ants in the same community; but I I:I existence in the same community of two or three defined castes of workers or sterile female ants; but 12 With respect to the almost universal sterility of species when first crossed, which forms so remarkable a contrast with the almost universal fertility of varieties when crossed, I must refer the reader to the recapitulation of the facts given at the end of the eighth chapter, which seem to me conclusively to show that this sterility is no more a special endowment than is the incapacity of two trees to be grafted together; but that it is incidental on constitutional differences in the reproductive systems of the intercrossed species. I2:d two distinct trees/on differences confined to the reproductive I2:f end of the ninth chapter/distinct kinds of trees 13 We see the truth of this conclusion in the vast difference in the result, when the same two species are crossed reciprocally; that is, when one species is first used as the father and then as the mother. I3:d reciprocally...