Contributions to the theory of natural selection : a series of essays / by Alfred Russel Wallace ...

  • Wallace, Alfred Russel, 1823-1913.
Date:
1870
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Contributions to the theory of natural selection : a series of essays / by Alfred Russel Wallace ... Source: Wellcome Collection.

    29/218 page 9
    THE INTRODUCTION OF NEW SPECIES. 9 wns given by the admirable paper of the lamented Mr. Strickland, published in the Annals of Na¬ tural History, in which he so clearly showed the true synthetical method of discovering the Natural System. Geographical Distribution of Organisms. If we now consider the geographical distribu¬ tion of animals and plants upon the earth, we shall find all the facts beautifully in accordance with, and readily explained by, the present hypo¬ thesis. A country having species, genera, and whole families peculiar to it, will be the neces¬ sary result of its having been isolated for a long period, sufficient for many series of species to have been created on the type of pre-existing ones, which, as well as many of the earlier- formed species, have become extinct, and thus made the groups appear isolated. If in any case the antitype had an extensive range, two or more groups of species might have been formed, each varying from it in a different manner, and thus producing several representative or analogous groups. The Sylviadse of Europe and the Sylvicolidae of North America, the Heliconidae of South America and the Euplœas of the East, the group of Tro- gons inhabiting Asia, and that peculiar to South America, are examples that may be accounted for in this manner. Such phaenomena as are exhibited by the Gala-
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