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Updated: May 17, 2025
In the Galapagos Archipelago, many even of the birds, though so well adapted for flying from island to island, are distinct on each; thus there are three closely-allied species of mocking-thrush, each confined to its own island.
We thus see that in closely-allied birds ornaments of the same kind have been gained by the males through the development of widely different feathers. It is a curious fact that the feathers of species belonging to very distinct groups have been modified in almost exactly the same peculiar manner.
During the day we saw several guanacos, and the track of the closely-allied species, the Vicuna: this latter animal is pre-eminently alpine in its habits; it seldom descends much below the limit of perpetual snow, and therefore haunts even a more lofty and sterile situation than the guanaco.
The pottery of this province is remarkably homogeneous in character, and we are warranted in assigning it to a single period of culture, and, in concluding, that the peoples who developed and practiced the art belonged to a group of closely-allied tribes. We can also state without fear of precipitating a controversy that the people who made this pottery were "mound-builders."
As he extends the range of his observations he will meet with more cases of difficulty; for he will encounter a greater number of closely-allied forms.
We have every reason to believe that many of these doubtful and closely-allied forms have permanently retained their characters in their own country for a long time; for as long, as far as we know, as have good and true species.
That it is this sex which has been chiefly modified, we may infer from the fact that, in almost every genus where the sexes differ, the males differ much more from one another than do the females; this is well shewn in certain closely-allied representative species, in which the females can hardly be distinguished, whilst the males are quite distinct.
But it may be urged that when several closely-allied species inhabit the same territory we surely ought to find at the present time many transitional forms.
It would be almost superfluous to adduce evidence in support of the above statement, that specific characters are more variable than generic; but I have repeatedly noticed in works on natural history, that when an author has remarked with surprise that some important organ or part, which is generally very constant throughout large groups of species, has differed considerably in closely-allied species, that it has, also, been variable in the individuals of some of the species.
The formula may be true to this extent, that the conditions favoring the appearance of one species may have equally favored what we call a closely-allied species. But even in this case, the material sequence is lost, and we have nothing to express a relationship as from parent to progeny.
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