Origin of Species Variorum

Comparison with 1872

Text in this page (from paragraph 3900, sentence 620, word 23 to paragraph 3900, sentence 800, word 13) is not present in 1872

As all the species of the same genus are supposed to be descended from a common parent, it might be expected that they would occasionally vary in an analogous manner; so that a variety of one species would resemble each other, or that a variety of one species would resemble in certain characters another and distinct species,— this other species being, on my view, only a well-marked and permanent variety. But characters exclu- sively due to analogous variation would probably be of an unimportant nature, for the preservation of all functionally important characters will have been determined through natural selection, in accordance with the diverse habits of the species. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... It might further be expected that the species of the same genus would occasionally exhibit reversions to long lost characters. As, however, we do not know the ... common ancestor of any natural group, we cannot distinguish between reversionary and analogous characters. If, for instance, we did not know that the parent rock-pigeon was not feather-footed or turn-crowned, we could not have told, whether such characters in our domestic breeds were reversions or only analogous variations; but we might have inferred that the blueness was a case of reversion, from the number of the markings, which are correlated with the blue tint, and which would not probably have all appeared together from simple variation. More especially we might have inferred this, from the blue colour and marks so often appearing when differently coloured breeds are crossed. Hence, though under nature it must generally be left doubtful, what cases

useless or rudimentary organs being thus transmitted. A mere tendency to produce a rudiment is indeed sometimes inherited. ↑

As all the species of the same genus are supposed, on our theory, to be descended from a common progenitor, it might be expected that they would occasionally vary in an analogous manner; so that the varieties of two or more species would resemble each other, or that a variety of some one species would resemble in certain characters another and distinct species, — this other species being according to our view only a well-marked and permanent variety. But characters thus gained would probably be of an unimportant nature, for the presence of all important characters will be governed by natural selection, in accordance with the different habits of the species, and will not be left to the mutual action of the nature of the organism and of the conditions of life. It might further be expected that the species of the same genus would occasionally exhibit reversions to long lost ancestral characters. As, however, we never know the exact character of the common ancestor of a natural group, we could not distinguish these two cases: if, for instance, we did not know that the rock-pigeon was not feather-footed or turn-crowned, we could not have told, whether these characters in our domestic breeds were reversions or only analogous variations; but we might have inferred that the blue colour was a case of reversion from the number of the markings, which are correlated with this tint, and which it does not appear probable would all appear together from simple variation. More especially we might have inferred this, from the blue colour and the several marks so often appearing when distinct breeds of distinct colours are crossed. Hence, although under nature it must generally be left doubtful, what cases