Some of the later socialists see in the theory of evolution associated with the name of Darwin a suitable expression of their ideas of development. Followers of Marx have found special points of attraction in Darwinism. Darwin himself was, of course, not a materialist; but many speculators have not unreasonably recognised in his teachings an affinity with materialism, which obviously accorded well with the materialistic conception of history held by Marx. The struggle of classes, which Marx regards as the key to history, is, we need not say, also an allied feature. But the Darwinian conception of development has to many students suggested the strongest reasons for doubt and hostility with reference to socialism. How does the theory of the struggle for existence consist with the harmony of interests contemplated by socialism? Is it not utopian of the Marx school to believe that the struggle of classes, which has hitherto characterised the course of history, can be brought to a close by a great revolutionary act? Competition, that _bête noire_ of the socialists, is simply the social-economic form of the struggle for existence. Is not competition, therefore, the prime condition of social progress? And is not socialism, therefore, inconsistent with progress? Thus we are confronted with the twofold problem, whether socialism does not deny the cardinal principles of evolution, and thereby also deny the prime condition of social progress? These questions are of considerable complexity. And their import will be better understood it we consider them in relation to another question with which they are intimately connected, and which is even more fundamental—the population question. The Darwinian theory of evolution rests on the Malthusian theory of population, and can be fully appreciated only by reference to it. In this place we need not discuss the theory of population as a whole, but merely in so far as it bears on our present inquiry. The theory of Malthus is so remarkable for its simplicity that no worthy excuse can be offered for the misconceptions regarding it which have been prevalent. The seeds of life, so runs the theory of Malthus, have been scattered throughout the world with a profuse and liberal hand. All living things tend to multiply indefinitely. Animals—even the least prolific—would, if their increase were not checked, fill the entire world. But as the means of subsistence are limited, the struggle for existence inevitably ensues, which is obviously all the more intense because so many animals are themselves the means of subsistence to others.