coast of Africa, some of them being not more than fifty miles distant. The Madeira group are to the northwest of the Canaries, and about four hundred miles from Morocco. The Azores are still farther in the same direction, being in the mid-Atlantic, nearly a thousand miles west from Lisbon. These islands are of volcanic origin, and all rise out of the ocean from a depth of from five thousand to eighteen thousand feet of water. It is therefore improbable that they ever had any land connection with the continent. Now, according to the general rule regarding the animals inhabiting islands thus situated, there are no native batrachians on them and no mammals, except bats, though the conditions are admirably fitted to sustain numerous species of mammals when once they are introduced; and frogs have become a nuisance in Madeira and the Azores. The only indigenous species of animals, beside the land mollusks, are birds, bats, butterflies, and beetles, whose presence can be accounted for by their power of flight when aided by the furious storms which sometimes sweep outward from the continent. In nearly every case this animal life has its closest affinities with the species of Europe and Northern Africa. Of the two hundred and thirty-six genera of beetles from the Madeira group, forty-four are peculiar to the Atlantic islands. "Most of them are, however, closely allied to European genera, of which they

are evidently modifications." A most striking fact regarding these genera of beetles is the prevalence of wingless varieties. "This is especially the case with groups which are confined to the Atlantic islands, many of which consist wholly of wingless species; but it also affects the others- no less than twenty-two genera of which are usually or sometimes winged in Europe having only wingless species in Madeira; and even the same species which is winged in Europe becomes, in at least three cases, wingless in Madeira, without any other perceptible change having taken place. But there is another most curious fact noticed by Mr. Wollaston that those species which possess wings in Madeira often have them rather larger than their allics in Europe."

In searching for an explanation it is easy to see that with beetles on a stormy island the absence of wings may be an advantage; for if the beetle has no wings he will not use them. If he possesses only moderately strong wings, more likely than not he will be using them when a storm is arising, which will blow him into the sea, and he will be drowned. If, however, he has unusually strong wings he may get back; and so, as is frequently the case, the individuals of the middling sort will drop out of existence, since they do not have the advantage of either extreme.

There are two methods by which to attempt an

explanation of these complicated facts; one of which is that these beetles were directly adapted to their conditions of existence by an act of immediate creation. This would account for the wingless condition of some and the superior power of wing in others, since these are both, though for opposite reasons, real advantages. But the hypothesis of direct creation does not explain the existence of rudimentary wings in many species, and the conformity in pattern of them all to that of beetles on the nearest continent. On the contrary, the hypothesis of indirect creation of species by natural selection, through " descent with modifications" accounts for all the elements of the problem, and furnishes no less evidence of design. Common descent from European forms explains the affinity with those forms.

Another fact equally impressive with the foregoing is to be found in the direction and character of the boundary line between the fauna of Asia and that of Australia. The Philippine Islands, with Sumatra, Java, and Borneo, are in a sea that is nowhere more than six hundred feet deep. So that with an elevation of the Malay archipelago to that amount, the continent of Asia would extend as far southeast as the island of Java, or twelve degrees of latitude beyond the Malay peninsula. Beyond a line drawn from the southeast end of Java to the southernmost of the Philippine

Islands the depth of the ocean is more than six hundred feet. According to Mr. Wallace,1 the line of soundings of six hundred feet, marking the termination of shallow seas, between the IndoMalayan and the Austro-Malayan regions, is also the boundary between Australian and Asiatic genera of plants and animals, though in one instance the islands of these different zoological provinces are within sight of each other. The animals and plants of Asia are supposed to have migrated to the farthest islands in the shallow seas of the Malay Archipelago when they were continuously connected by land now moderately submerged; while the Marsupials of Australia maintained their ground on the islands that are now, and probably have been from a very remote period, surrounded by deep water.

Thus the principle is pretty well established that, with little regard to natural conditions, the fauna of islands is more nearly allied to that of the nearest continent than to that of any other region, and that the deeper the sea between them the more diverse is the fauna.2

This class of facts is naturally explained on the supposition that the Creator has given to the lifeprinciple a power co-ordinate with that of the con

1 See "The Malay Archipelago," pp. 20-31. Also Lyell's

Principles of Geology, Vol. ii. pp. 349, 350.

2 The preceding illustrations are mainly drawn from Wallace's Geographical Distribution of Animals" and "Island Life.”

ditions of existence. The changes in the forms of life follow a long way behind the changes in the physical conditions. The islands surrounded by deep water are supposed to have retained the earlier forms of life because they have been longer isolated, and the conditions have there been more uniform, and there has been less room for competition between varieties.

The full bearing of these facts cannot, however, be seen till they are joined with two or three other co-ordinate series of phenomena. We proceed, therefore, to speak

VII. Of the Distribution of Species in Time.

As long ago as 1844, Professor Owen enunciated the law" that with extinct as with existing Mammalia, particular forms were assigned to particular provinces, and that the same forms were restricted to the same provinces at a former geological period as they are at the present day."1 In 1861, he added: "That period was the more recent Tertiary one. In carrying back the retrospective comparison of existing and extinct Mammals to those of the Eocene and Oölitic strata, in relation to their local distribution, we obtain indications of extensive changes in the relative position of sea and land during these epochs, in the degree of

1 Quoted from Transactions of the British Association, 1844, in Owen's Palaeontology, p. 433.