The insect fauna of the Galapagos islands is scanty, and chiefly composed of beetles. These number 35 species, which are nearly all peculiar, and in some cases go to constitute peculiar genera. The same remarks apply to the twenty species of land-shells. Lastly, of the total number of flowering plants (332 species) more than one half (174 species) are peculiar. It is observable in the case of these peculiar species of plants—as also of the peculiar species of birds—that many of them are restricted to single islands. It is also observable that, with regard both to the fauna and flora, the Galapagos Islands as a whole are very much richer in peculiar species than either the Azores or Bermudas, notwithstanding that both the latter are considerably more remote from their nearest continents. This difference, which at first sight appears to make against the evolutionary interpretation, really tends to confirm it. For the Galapagos Islands are situated in a calm region of the globe, unvisited by those periodic storms and hurricanes which sweep over the North Atlantic, and which every year convey some straggling birds, insects, seeds, &c., to the Azores and Bermudas. Notwithstanding their somewhat greater isolation geographically, therefore, the Azores and Bermudas are really less isolated biologically than are the Galapagos Islands; and hence the less degree of peculiarity on the part of their endemic species. But, on the theory of special creation, it is impossible to understand why there should be any such correlation between the prevalence of gales and a comparative inertness of creative activity. And, as we have seen, it is equally impossible on this theory to understand why there should be a further correlation between the degree of peculiarity on the part of the isolated species, and the degree in which their nearest allies on the mainland are there confined to narrow ranges, and therefore less likely to keep up any biological communication with the islands.

St. Helena.—A small volcanic island, ten miles long by eight wide, situated in mid-ocean, 1100 miles from Africa, and 1800 from South America. It is very mountainous and rugged, bounded for the most part by precipices, rising from ocean depths of 17,000 feet, to a height above the sea-level of nearly 3,000. When first discovered it was richly clothed with forests; but these were all destroyed by human agency during the 16th, 17th and 18th centuries. The records of civilization present no more lamentable instance of this kind of destruction. From a merely pecuniary point of view the abolition of these primeval forests has proved an irreparable loss; but from a scientific point of view the loss is incalculable. These forests served to harbour countless forms of life, which extended at least from the Miocene age, and which, having found there an ocean refuge, survived as the last remnants of a remote geological epoch. In those days, as Mr. Wallace observes, St. Helena must have formed a kind of natural museum or vivarium of archaic species of all classes, the interest of which we can now only surmise from the few remnants of those remnants, which are still left among the more inaccessible portions of the mountain peaks and crater edges. These remnants of remnants are as follows.

There is a total absence of all indigenous mammals, reptiles, fresh-water fish, and true land-birds. There is, however, a species of plover, allied to one in South Africa; but it is specifically distinct, and therefore peculiar to the island. The insect life, on the other hand, is abundant. Of beetles no less than 129 species are believed to be aboriginal, and, with one single exception, the whole number are peculiar to the island. “But in addition to this large amount of specific peculiarity (perhaps unequalled anywhere else in the world), the beetles of this island are remarkable for their generic isolation, and for the altogether exceptional proportion in which the great divisions of the order are represented. The species belong to 39 genera, of which no less than 25 are peculiar to the island; and many of these are such isolated forms that it is impossible to find their allies in any particular country[24].” More than two-thirds of all the species belong to the group of weevils—a circumstance which serves to explain the great wealth of beetle-population, the weevils being beetles which live in wood, and St. Helena having been originally a densely wooded island. This circumstance is also in accordance with the view that the peculiar insect fauna has been in large part evolved from ancestors which reached the island by means of floating timber; for, of course, no explanation can be suggested why special creation of this highly peculiar insect fauna should have run so disproportionately into the production of weevils. About two-thirds of the whole number of beetles, or over 80 species, show no close affinity with any existing insects, while the remaining third have some relations, though often very remote, with European and African forms. That this high degree of peculiarity is due to high antiquity is further indicated, according to our theory, by the large number of species which some of the types comprise. Thus, the 54 species of Cossonidæ may be referred to three types; the 11 species of Bembidium form a group by themselves; and the Heteromera form two groups. “Now, each of these types may well be descended from a single species, which originally reached the island from some other land; and the great variety of generic and specific forms into which some of them have diverged is an indication, and to some extent a measure, of the remoteness of their origin[25].” But, on the counter-supposition that all these 128 peculiar species were separately created to occupy this particular island, it is surely unaccountable that they should thus present such an arborescence of natural affinities amongst themselves.

Passing over the rest of the insect fauna, which has not yet been sufficiently worked out, we next find that there are only 20 species of indigenous land-shells—which is not surprising when we remember by what enormous reaches of ocean the island is surrounded. Of these 20 species no less than 13 have become extinct, three are allied to European species, while the rest are so highly peculiar as to have no near allies in any other part of the globe. So that the land-shells tell exactly the same story as the insects.

Lastly, the plants likewise tell the same story. The truly indigenous flowering plants are about 50 in number, besides 26 ferns. Forty of the former and ten of the latter are peculiar to the island, and, as Sir Joseph Hooker tells us, “cannot be regarded as very close specific allies of any other plants at all” Seventeen of them belong to peculiar genera, and the others all differ so markedly as species from their congeners, that not one comes under the category of being an insular form of a continental species. So that with respect to its plants no less than with respect to its animals, we find that the island of St. Helena constitutes a little world of unique species, allied among themselves, but diverging so much from all other known forms that in many cases they constitute unique genera.

Sandwich Islands.—These are an extensive group of islands, larger than any we have hitherto considered—the largest of the group being about the size of Devonshire. The entire archipelago is volcanic, with mountains rising to a height of nearly 14,000 feet. The group is situated in the middle of the North Pacific, at a distance of considerably over 2,000 miles from any other land, and surrounded by enormous ocean depths. The only terrestrial vertebrata are two lizards, one of which constitutes a peculiar genus. There are 24 aquatic birds, five of which are peculiar; four birds of prey, two of which are peculiar; and 16 land-birds, all of which are peculiar. Moreover, these 16 land-birds constitute no less than 10 peculiar genera, and even one peculiar family of five genera. This is an amount of peculiarity far exceeding that of any other islands, and, of course, corresponds with the great isolation of this archipelago. The only other animals which have here been carefully studied are the land-shells, and these tell the same story as the birds. For there are no less than 400 species which are all, without any exception, peculiar; while about three-quarters of them go to constitute peculiar genera. Again, of the plants, 620 species are believed to be endemic; and of these 377 are peculiar, yielding no less than 39 peculiar genera.

Prejudice apart, I think we must all now agree that it is needless to continue further this line of proof. I have chosen the smallest and most isolated islands for the purposes of our present argument, first because these furnish the most crucial kind of test, and next because they best admit of being dealt with in a short space. But, if necessary, a vast amount of additional material could be furnished, not only from other small oceanic islands, but still more from the largest islands of the world, such as Australia and New Zealand. However, after the detailed inventories which have now been given in the case of some of the smaller islands most remote from mainlands, we may well be prepared to accept it as a general law, that wherever there is evidence of land-areas having been for a long time separated from other land-areas, there we meet with a more or less extraordinary profusion of unique species, often running up into unique genera. And, in point of fact, so far as naturalists have hitherto been able to ascertain, there is no exception to this general law in any region of the globe. Moreover, there is everywhere a constant correlation between the degree of this peculiarity on the part of the fauna and flora, and the time during which they have been isolated. Thus, for instance, among the islands which I have called into evidence, those that are at once the most isolated and give independent proofs of the highest antiquity, are the Galapagos Islands, the Sandwich Islands, and St. Helena. Now, if we apply the method of tabular analysis to these three cases, we obtain the following most astonishing results. For the sake of simplicity I will omit the enumeration of peculiar genera, and confine attention to peculiar species. Moreover, I will consider only terrestrial animals; for, as we have already seen, aquatic animals are so much more likely to reach oceanic islands that they do not furnish nearly so fair a test of the evolutionary hypothesis.

PECULIAR SPECIES.
Shells.Insects.Reptiles.Birds.Mammals.
Sandwich400?2160
Galapagos153510300
St. Helena20128010
Totals.43516312470
NON-PECULIAR SPECIES.
Shells.Insects.Reptiles.Birds.Mammals.
Sandwich0?000
Galapagos??010
St. Helena0?000
Totals.0?010