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work has grown out of the recent progress of biological science, and could neither have been produced earlier than it has been, nor probably by any other living author. To those who regard the evolution hypothesis as a piece of mere useless speculation, it may be replied that it is the most powerful stimulus to investigation in the higher science of living things that has yet been known, of which the noble work before us is incontestable proof. The problem of animal distribution is here so conceived and presented as to give it very much the character of a new subject.

Up to this time, a naturalist has only needed to try to learn about the fauna of any country to be made aware of our lack of knowledge in this field. Much has been learned, of course, but the records were fragmentary and scattered, and it was only on the shelves of the best zoological libraries that anything approaching completeness was to be found, so that practically such information has been inaccessible. But with the growing interest in Darwinism there came an appreciation of the value of the study of distribution, and a demand arose which made itself felt. As is always the case, the demand only needed to become urgent to insure a supply. And it was to meet this want, growing daily more pressing, that Mr. Wallace put forth this work—and the task could not have fallen into better hands. His life has been one of preparation for it. As early as 1848 he embarked with Mr. H. W. Bates for the Amazons, and in that region—the richest in animal life and later in the Malay Archipelago, the best years of his life were given to the study of zoölogy. Few of our readers need to be reminded that in those far-away lands he independently worked out the theory of "natural selection." The more difficult work of establishing the validity of the "doctrine of descent" fell into other and, as Mr. Wallace modestly and gracefully says, abler hands; but he has not ceased to work in that field, and has given great aid in searching out relevant facts and showing their bearings. This work is certainly one of the most valuable of these contributions. From the scattered sources he has, with infinite pains, collected the details of that which was known, and, arranging them with a skill and method which leave little to be desired, has put them within the reach of all.

The book sets out with an introductory chapter, showing the inadequacy of the popular notion that the manner in which animals are dispersed over the globe is due to diversities of climate and vegetation. Much as there undoubtedly is to give rise to this belief, a little examination shows that no such off-hand treatment will do. That South Africa has lions and giraffes, and Australia kangaroos and other marsupials, finds no explanation in differences of soil and climate, because no marked differences exist. So, too, the theory fails when we find Europe destitute of raccoons, opossums, and humming-birds, and North America without hedgehogs or true flycatchers, although the conditions of life are in all essentials similar in the two regions.

Assuming the view that each species