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Show 392 ISLAND LIFE. (L'Alt'l' II. important a part of the fauna of Madagascar as well as of Africa, were abundant in Europe throughout the ~vhole Tertiary period, but are not known to have ever lived m. an! part of the American continent. We here see the apphcatwn of the principle which we have already fully proved and il.lustrated (Chapter IV., p. 62), that all extensive groups have a w1de range at the period of their maximum development ; but as t.hey decay their area of distribution diminishes or breaks up mto detached fracrments which one after another disappear till the 0 ' group becomes extinct. Those animal forms which we now find isolated in Madacrascar and other remote portions of the 0 • globe all belong to ancient groups which are in a decaymg or nearly extinct condition, while those which are absent from it belong to more recent and more highly-developed types, which range over extensive and continuous areas, but have bad no opportunity of reaching the more ancient continental islands. Anomalies of Distribution and how to explain them.-If these considerations have any weight, it follows that there is no reason whatever for .supposing any former direct connection between Madagascar and the Greater Antilles merely because the Insectivorous Centetidre now exist only in these two groups of islands; for we know that the ancestors of this family must once have had a much wider range, which almost certainly extended over the great northern continents. We might as reasonably suppose a land-connection across the Pacific to account for the camels of Asia having their nearest existing allies in the llamas and alpacas of the Peruvian Andes, and another between Sumatra and Brazil, in order that the ancestral tapir of one country might have passed over to the other. In both these cases we have ample proof of the former wide extension of the group. Extinct camels of numerous species abounded in North America in Miocene, Pliocene, and even Post-pliocene times, and one bas also been found in N ortbwestern India, but none whatever among all the rich deposits of mammalia in Europe. We are thus told, as clearly as possible, that from the North American continent as a centre the camel tribe spread westward, over now-submerged land at the shallow Behring Straits and Kamschatka Sea, into Asia, and CHAP. XIX.] 'l'IH~ MADAGASCAR GROUP. 3!J3 southward along the Andes into South America. Tapirs are even more interesting and instructive. Their remotest known ancestors appear in Western Europe in the early portion of the Eocene period ; in the later Eocene and the Miocene other forms occur both in Europe and North America. These seem to have become extind in North America, while in Europe they developed largely into many forms of true tapirs, which at a muoh later period found their way again to North, and thence to South, America, where their remains are found in caves and gravel-deposits. It is an instructive fact that in the Eastern continent, where they '"'ere once so abundant, they have dwindled down to a single species, existing in small numbers in the Malay Peninsula, Sumatra, and Borneo only; while in the Western continent, where they are comparatively recent immigrants, they occupy a much larger area, and are represented by three or four distinct species. Who could possibly have imagined such migrations, and extinctions, and changes of distribution as are demonstrated in the case of the tapirs, if we had only the distribution of the existing species to found an opinion upon? Such cases as these-and there are many others equally striking-show us with the greatest distinctness how nature has worked in bringing about the examples of anomalous distribution that everywhere meet us; and we must, on every ground of philosophy and common sense, apply the same method of interpretation to the more numerous instances of anomalous distribution we discover among such groups as reptiles, binls, and insects) where we rarely have any direct evidence of their past migrations through the discovery of fossil remains. Whenever we can trace the past history of any group of terrestrial animals, we invariably find that its actual distribution can be explained by migrations effected by means of comparatively slight modifications of our existing continents. 1 n no single case have we any direct evidence that the distribution of land and sea has been radically changed during the whole lapse of the Tertiary and Secondary periods, while, as we have already shown in onr fifth chapter, the testimony of geology itself: if fairly interpreted, upholds the same theory of the stability of our continents and the permanence of our oceans. Yet so ea~y |