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For instance, two varieties of the same species inhabit America and Europe, and the species in such genera have on an average a very wide range; for this will largely depend on how far the process of modification has gone; for instance, two varieties of the same species inhabit America and Europe, and thus the species has an immense range; but, if variation were to be carried a little further, the two varieties would be ranked as distinct species, and their range would be greatly reduced. Still less is it meant, that .. species which have the capacity of crossing barriers and ranging widely, as in the case of certain powerfully-winged birds, will necessarily range widely; for we should never forget that to range widely implies not only the power of crossing barriers, but the more important power of being victorious in distant lands in the struggle for life with foreign associates. But according to the view that all the species of a genus, though distributed to the most remote points of the world, are descended from a single progenitor, we ought to find, and I believe as a general rule we do find, that some at least of the species range very widely. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
Text in this page (from paragraph 2300, sentence 010 to paragraph 2300, sentence 100, word 44) is not present in 1872
Nor is it meant that the species have on an average a very wide range; for this will largely depend on how far the process of modification has gone; for instance, two varieties of the same species inhabit America and Europe, and the species thus has an immense range; but, if the variation had been carried a little further, the two varieties would have been ranked as distinct species, and the range would have been greatly reduced. Still less is it meant, that a species which apparently has the capacity of crossing barriers and ranging widely, as in the case of certain powerfully-winged birds, will necessarily range widely; for we should never forget that to range widely implies not only the power of crossing barriers, but the more important power of being victorious in distant lands in the struggle for life with foreign associates. But on the view of all the species of a genus having descended from a single parent, though now distributed at the most remote points of the world, we ought to find, and I believe as a general rule we do find, that some at least of the species range very widely; for it is necessary that the unmodified parent should have ranged widely, undergoing modification during its diffusion, and should have placed itself under diverse conditions favourable for the conversion of its offspring, first into new varieties and ultimately into new species. ↑
In considering the wide distribution of certain genera, we should bear in mind that some of them are extremely ancient, and that their species will have branched off from a common progenitor at a remote epoch; so that in these cases there will have been ample time for great climatal and geographical changes and for accidents of transport; consequently for the migration of some of the species into all quarters of the world, where they will have become slightly modified in relation to their new conditions.