_Conclusion._--I must now conclude this very imperfect sketch of a few of the offshoots from the great tree of Biological study. It will, perhaps, be thought by some that my remarks have tended to the depreciation of our science, by hinting at imperfections in our knowledge and errors in our theories where more enthusiastic students see nothing but established truths. But I trust that I may have conveyed to many of my hearers a different impression. I have endeavoured to show that, even in what are usually considered the more trivial and superficial characters presented by natural objects, a whole field of new inquiry is opened up to us by the study of distribution and local conditions. And as regards man, I have endeavoured to fix your attention on a class of facts which indicate that the course of his development has been far less direct and simple than has hitherto been supposed; and that, instead of resembling a single tide with its advancing and receding ripples, it must rather be compared to the progress from neap to spring tides, both the rise and the depression being comparatively greater as the waters of true civilisation slowly advance towards the highest level they can reach. And if we are thus led to believe that our present knowledge of nature is somewhat less complete than we have been accustomed to consider it, this is only what we might expect; for however great may have been the intellectual triumphs of the nineteenth century, we can hardly think so highly of its achievements as to imagine that, in somewhat less than twenty years, we have passed from complete ignorance to almost perfect knowledge on two such vast and complex subjects as the Origin of Species and the Antiquity of Man. VIII. THE DISTRIBUTION OF ANIMALS AS INDICATING GEOGRAPHICAL CHANGES.[63] Old Opinions on Continental Changes--Theory of Oceanic Islands--Present and Past Distribution of Land and Sea--Zoological Regions--The Palæarctic Region--The Ethiopian Region--The Oriental Region--Past Changes of the Great Eastern Continent--Regions of the New World--Past History of the American Continents--The Australian Region--Summary and Conclusion. [63] This is one of the Lectures on Scientific Geography delivered before the Royal Geographical Society, but the introductory portion has been rewritten. The original Lecture appeared in the _Proceedings_ of the Society for September, 1877, under the title: “On the Comparative Antiquity of Continents, as indicated by the Distribution of Living and Extinct Animals.”