held to have much weight on the present question. Then there is the solitary monkey, but as that actually inhabits Europe, we need hardly have included it among the representatives of Ethiopian groups, except to give all the facts that can be fairly claimed on that side. The antelope is a desert-haunting species, and therefore may be looked upon as a straggler on the northern side of the Sahara; and, besides these, we have representatives of two really African genera (Macroscelides and Zorilla), giving a total of only eight species as the measure of Ethiopian affinity. The remaining species, seven in number, are true desert-haunters, roaming over N. Africa, Egypt, and Arabia, into the Indian deserts, and have scarcely any more right to be considered as belonging to one region than another, since they inhabit the district which forms the boundary and debateable land of the Ethiopian, Indian, and Palæarctic regions.

It would seem, therefore, that the supposed discrepancy of the Mammalia, in determining the Southern limit of the Palearctic province, is altogether imaginary. The number of species absolutely identical is not so great as in the birds; but Europe is not the whole Palearctic province, and if we take genera instead of species, we shall find the correspondence as complete as possible,-28 genera being truly Palearctic, only 3 Ethiopian, while 5 are Asiatic, or desertdwellers. In this case, therefore, the whole of the vertebrata combine with the insects, the land shells, and the plants, to place N. Africa in the Palearctic region.

The case of the insects in the Australian portion of the Malay Archipelago is one of much greater difficulty. Australia itself contains a remarkable assemblage of insects, among which its Lamellicornes, Buprestidae, and Curculionidae offer a number of striking forms and genera quite peculiar to it. In New Guinea and the Moluccas, on the other hand, Lamellicornes are comparatively scarce, and with the Buprestide and Curculionida are of Indian rather than Australian genera; while the great family of the Anthribide, which is almost entirely absent in Australia, is here everywhere abundant in genera, species and individuals, though less so than in the western or Indian region.

To account for this remarkable discrepancy we must consider:— 1st, that insects are much more immediately dependent on the character of the vegetation, and therefore on climate, than are vertebrated animals; and 2ndly, that water-barriers are much less effective in preventing their dispersion. A narrow strait is an effectual bar

to the migration of mammals, and of many reptiles and birds, while insects may be transported in the egg and larva state by floating timber, and from their small size and great powers of flight may be easily carried by the winds from one island to another. Now the characteristic insects of Australia seem specially adapted to a dry climate and a shrubby flower-bearing vegetation, and could hardly exist in the excessively moist atmosphere and amid the dense flowerless forests of the equatorial islands. If, therefore, we suppose Australia itself to be the most ancient portion of this region (which its great richness in peculiar generic forms seems to indicate), we can easily understand how, when the islands of the Moluccas and New Guinea first rose above the waters and became clothed with dense forests nurtured by tropical heat and perpetual moisture, though the birds and mammals readily adapted themselves to the new conditions, the insects could not do so, but gave way before the immigrants from the islands to the west of them, which having been developed under similar climatal conditions, and thus become specially adapted to them, were enabled by the enormous powers of multiplication and dispersion possessed by insects, at once to establish themselves in the newly formed lands, and develop an insect population in many respects at variance with other classes of animals.

There are, however, several instances of groups of insects almost as strictly confined to one half of the Archipelago as is so remarkably the case with the vertebrata ; and when the extensive collections made by myself in most of the islands come to be accurately worked out, no doubt more such instances will be found. Among Coleoptera I may mention the Tmesisternina, a remarkable sub-family of Longicornes, as being strictly confined to the Australian region, over the whole of which it extends, and has its western limit in Celebes along with the Marsupials and the Trichoglossi. Again, Mr. Baly, so well known for his acquaintance with the Phytophagous Coleoptera, finds that one of the principal sub-families of that tribe (Adoxina) which he has recently classified, though spread over Europe and the whole of Asia, is only found in the Archipelago in those islands which belong to the Indian region of zoology. This proves that there is an ancient insect-population in the Austro-Malayan Islands which accords in its distribution with the other classes of animals, but which has been overwhelmed, and in some cases perhaps exterminated by immigrants from the adjacent countries. The result is a mixture of races in which the foreign element is in excess; but naturalists

need not be bound by the same rule as politicians, and may be permitted to recognise the just claims of the more ancient inhabitants, and to raise up fallen nationalities. The aborigines and not the invaders must be looked upon as the rightful owners of the soil, and should determine the position of their country in our system of Zoological geography.

My friend, Mr. Bates, has kindly furnished me with some facts as to the entomology of Chili and south temperate America, which would show that the insects of this region have very little connection with those of tropical America.

Out of 10 genera of butterflies found in Chili, not one is characteristic of tropical America. Four (Colias, Argynnis, Erebia, and Satyrus) are northern forms, only one of which occurs at all in tropical America, and that high up in the Andes; 3 others are peculiar to Chili, but have decided north temperate or Arctic affinities; and 3 more (Anthocharis, Lycana, and Polyommatus) are cosmopolitan, but far more abundant in temperate than tropical regions. Judging, therefore, from butterflies only we should decidedly have to place south temperate America in the Nearctic region, or form it into a region by itself.

Two important families of Coleoptera, the Geodephaga and the Lamellicornes, furnish different but equally remarkable results. There are 77 genera of these families found in Chili, of which 46 are peculiar to south temperate America, being 3ths of the whole; 17 are cosmopolitan, 2 are north temperate, 10 tropical American, and 1 is African. But of the 46 peculiar genera no less than 10 are closely allied to Australian forms, and 3 to South African, so that the affinities of these groups of coleoptera are almost as strong to Australia as to tropical America. Next comes South Africa, and lastly, the north temperate zone; though as the two genera Carabus and Geotrupes are very extensive and important, and are totally absent from the tropics, but appear again in Chili, the real amount of affinity to northern regions may be taken as somewhat larger.

Here then, as only 10 genera out of 77 are common to south temperate and tropical America, and as the remainder have wide spread affinities,-to the northern hemisphere, to Australia, and to South Africa, it would seem impossible from a consideration of these families of Coleoptera alone, not to separate the south temperate zone of South America as a distinct primary region.

Other orders of insects and other families of Coleoptera may very

probably give somewhat different results. From Boheman's work on the Cassidido I find that the genera of tropical America send representatives into Chili, and even into Patagonia, and that none of the south temperate forms have a direct affinity with those of Australia. But this family is almost exclusively tropical, very few and obscure species inhabiting the colder regions of the earth, while there are no generic forms peculiar to the Australian region.

In many of the preceding facts we have a most interesting correspondence with those furnished by the distribution of plants. Dr. Hooker has shown the large amount of resemblance between the floras of southern South America and Australia, especially Tasmania and New Zealand, one eighth of the whole New Zealand flora being identical with South American species. Again, the occurrence of northern genera of coleoptera in Chili and the whole of the butterflies having northern affinities agree with the number of northern genera and species of plants in Patagonia and Fuegia, and are additional proofs of the intensity and long continuance of the glacial epoch which sufficed to allow so many generic forms to pass the equator from north to south. We have here another illustration, how much easier of diffusion and how much more dependent on local conditions are insects than the higher animals. A great part of the southern portion of America is of more recent date than the central tropical mass, and must have had at one time a closer communication than at present with the antarctic lands and Australia, the insects and plants of which finding a congenial climate, established themselves in the new country, being only feebly opposed by the few northern forms which had already or soon after migrated there. And the fact that Tasmania and New Zealand are the poorest countries in the world in butterflies, will enable us to understand how it is that all those found in Chili are northern forms, while the coleoptera of the same countries (Tasmania and New Zealand) being tolerably abundant and varied, and having a shorter journey to perforin than the north temperate immigrants, were enabled to get the upper hand in colonizing the new country.

The marsupial Opossums are the most remarkable case of vertebrata in America having Australian affinities. It is very doubtful whether these could have been introduced in the same manner as the plants and insects already alluded to, because the latter have to a considerable extent an antarctic character, and do not appear in such numbers as to indicate an actual continuity of land, which would have been almost indispensable for the passage of mammalia, and

would at the same time have undoubtedly admitted Australian forms of land birds, which do not exist in South America. It seems more reasonable, therefore, to suppose that these Marsupials have inhabited America since the Eocene period, when the same genus existed in Europe, and the Marsupial order had probably a universal distribution.

With this one exception, the birds, the mammalia, and the reptiles of south temperate America have little or no affinity either with north temperate or Australian forms, but are modifications of the true denizens of the Neotropical regions. They appear to have been enabled rapidly to seize hold of the country, and to adapt themselves to its modified climate and physical features-a remarkable instance of which is mentioned by Mr. Darwin in the woodpecker of the Pampas, which never climbs a tree. The tropical insects, on the other hand, having become gradually specialized during long periods for a life amid continual verdure and unvarying summer, were totally unfitted for the new conditions presented to them, and only in a very few cases were able to struggle against forms already adapted to a more barren country and a more rigorous climate.

This difference in the adaptive capacity of groups, combined with an unequal power of diffusion, will cause the various kinds of barriers to be sometimes more and sometimes less effective. For example, when a mountain range has attained only a moderate elevation it will already completely bar the passage of many insects, while mammalia, birds, and reptiles, more capable of sustaining different conditions, will readily pass over it. On the other hand, an arm of the sea, or even a wide river, will completely isolate most mammals and many reptiles, while insects have still various means of passing it.

Another consideration which must help to determine the amount of specific peculiarity in a given region, is the average rate at which specific forms have changed. Paleontologists have determined that mammalia have changed much more rapidly than mollusca, from the phenomena of the comparatively recent extinction of so many species of mammals, whose remains are found along with existing species of sheils. From the evidence of the distribution of existing species, birds would appear to have changed at least as quickly as mammals, and insects, in some cases, perhaps more so; owing, no doubt, to their

Except the batrachians, which show some affinities between Australia and S. America, a case analogous to that of Japan.