The Geographical Distribution of Animals

EVERY one whose life has not been wholly spent within city walls must ha.ve observed that animal life varies greatly in the districts with which he is familiar. Different species are not found uniformly scattered over the surface of the country, but in different localities with similar features. Every country boy knows 'Postlethwaite Oaks' is the only place for miles round where he has a chance of capturing a Purple Emperor butterfly, or that if he visits ' Harkend Brook' at the proper season the chances are that he finds two or three kingfishers' nests. If we quit our own confined districts a.nd travel into other counties or countries, new kinds of animals appear; and the more extensive the range of our observation the greater the difference in the forms of animated life. If we ",houId be sufficiently curious or interested to ask ourselves 'Why should this be so l' we should probably feel satisfied with the obvious, though somewhat vague answer, that 'difterences of climate and vegetation demand animal life in harmony.' In all likelihood we should flot go a step farther back and w;k ouraelves: 'Have these peculiar species existed in these peculiar localities throughout:ill time '1' A modern naturalist however, could easily shew the insufficiency ;f this answer. He would point out that various regions of the world, closely resembling each other in both climate and vegetation, are nevertheless inhabited by very different kinds of animals. Thus the forests of Equatorial Africa teem with elephants, apes, leopards, guinea-fowls, and touracos ; while the similar arboreal regions of South America shew the tapir, the prehensile-tailed monkey, the jaguar, the curassow, and the toucan. Certain parts of Australia are remarkably like certain parts of Africa; but while the latter possess the mighty liou, the graceful zebra, and the tall giraffe, the former can produce nothing larger or more formidable than the kangaroo, the wombat, or the phalanger. Mauy large and important groups of animals are found restricted in their range in some way that cannot be accounted for merely by climate or soil Antelopes are found only in Africa and Asia; sloths only in South America; true lemurs are limited to Madagascar; birds-of-paradise to New Guinea. Acknowledging the cogency of this objection to our explanation of the facts, and now at the end of our resources, we should require to look beyond ourselves and our own range of knowledge for an answer. Respoll8ive to our look of inquiry up starts ?rrr Alfred Russel Wallace, of Malay Archipelago fame, and gives us, in two large and handsome volumes, a most learned and fascinating account of the distribution of animals throughout the world.· The reader need not fear that this work is too scientifically dry for any but the professed naturalist. The last part, it is true, consisting of a systematic sketch of the chief families of land-animals in their geographical relations, may well be left to the professional; but there is abundance of interesting reading in the other three sections of the book. Part first, in particular, treating of the general phenomena of distribution, we recommend everyone to peruse. Here we can do little more than indicate the theory of zoological distribution as set forth by!Ir Wallace, with a very few cullwgs from his interesting examples and details. Those who have studied the subject scientifioally have one factor to use in their answer to the question with which we started, not at the disposal of the ordinary observer. They deal with the problem of distribution not only with reference to the present, but with all the light that can be shed upon it from the past. Historical geolo~y gives most valuable aid in determining the -probable explanation of the distribution of living creatures. By attention to the varioUIJ geological strata we can reproduce the physical geography of the earth in the remotest time, Quoting from Geikie's Manual of Hiltorical Geology, issued by the publishers of this Joumal, we find that' vast changes in the relative position of land and st'a there have been; myriads of species of plants and animals have successively appeared, and then vanished for ever; the same climatic conditions have not always persisted in the same latitude, but ever and anon warm conditions of temperature have given place to cold, and vice 't·''I"Sa.' In particular, palroontology or the science of fO<l:!il animals, a branch of historical geology, is most useful, by giving the clearest indications of the fonner states of distribution. With due regard to materials lloth plL~t anll