Small and unimportant as are those little equatorial islands from the geographical and commercial point of view, they will yet remain for ever classic ground to the biologists of the future from their close connection with the master-problems of the 'Origin of Species.' Here more, perhaps, than anywhere else the naturalist of the 'Beagle' found himself face to face in real earnest with the ultimate questions of creation or evolution. A group of tiny volcanic islets, never joined to any land, nor even united to one another, yet each possessing its own special zoological features--the Galapagos roused to an extraordinary degree the irresistible questionings of Darwin's mind. They contain no frogs, and no mammal save a mouse, brought to them, no doubt, by some passing ship. The only insects are beetles, which possess peculiar facilities for being transported in the egg or grub across salt water upon floating logs. There are two kinds of snake, one tortoise, and four lizards; but, in striking contrast to this extreme poverty of terrestrial forms, there are at least fifty-five distinct species of native birds. A few snails complete the list. Now most of these animals, though closely resembling the fauna of Ecuador, the nearest mainland, are specifically distinct; they have varied (as we now know) from their continental types owing to natural selection under the new circumstances in which they have been placed. But Darwin had not yet evolved that potent key to the great riddle of organic existence. He saw the problem, but not its solution. 'Most of the organic productions,' he says plainly, 'are aboriginal creations, found nowhere else; there is even a difference between the inhabitants of the different islands: yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean, between 500 and 600 miles in width.... Considering the small size of these islands, we feel the more astonished at the number of their aboriginal beings, and at their confined range. Seeing every height crowned with its crater, and the boundaries of most of the lava-streams still distinct, we are led to believe that within a period geologically recent the unbroken sea was here spread out. Hence, both in space and time we seem to be brought somewhat nearer to that great fact--that mystery of mysteries--the first appearance of new beings on this earth.' Among the most singular of these zoological facts may be mentioned the existence in the Galapagos archipelago of a genus of gigantic and ugly lizard, the amblyrhyncus, unknown elsewhere, but here assuming the forms of two species, the one marine and the other terrestrial. In minuter points, the differences of fauna and flora between the various islands are simply astounding, so as to compel the idea that each form must necessarily have been developed not merely for the group, but for the special island which it actually inhabits.