The English reader will care to be instructed on the antithesis of Virchow and Haeckel which gives point to these lectures, and which is often misrepresented in this country. Virchow, the greatest pathologist and one of the leading anthropologists of Germany, had much to do with the inspiring of Haeckel's Monistic views in the fifties. Like several other prominent German thinkers, Virchow subsequently abandoned the positive Monistic position for one of agnosticism and scepticism, and a long and bitter conflict ensued. It is hardly too much to say that Virchow's ultra-timid reserve in regard to the evolution of man and other questions has died with him. Apart from one or two less prominent anthropologists, and the curious distinction drawn by Dr. A. R. Wallace, science has accepted the fact of evolution, and has, indeed, accepted the main lines of Haeckel's ancestral tree of the human race. In any case, Haeckel had the splendid revenge of surviving his old teacher and almost lifelong opponent. Berlin had for years been dominated by the sceptical temper of Virchow and Du Bois-Reymond. The ardent evolutionist and opponent of Catholicism was impatient of a reserve that he felt to be an anachronism in science and an effective support of reactionary ideas. It was, therefore, with a peculiar satisfaction that he received the invitation, after Virchow's death, to address the Berlin public. Among the many and distinguished honours that have been heaped upon him in the last ten years this was felt by him to hold a high place. He could at last submit freely, in the capital of his country, the massive foundations and the imposing structure of a doctrine which he holds to be no less established in science than valuable in the general cause of progress. The lectures are reproduced here not solely because of the interest aroused in them by the "Jesuit" telegram. They contain a very valuable summary of his conclusions, and include the latest scientific confirmation. Rarely has the great biologist written in such clear and untechnical phrases, so that the general reader will easily learn the outlines of his much-discussed Monism. To closer students, who are at times impatient of the Lamarckian phraseology of Haeckel--to all, in fact, who would like to see how the same evolutionary truths are expressed without reliance on the inheritance of acquired characters--I may take the opportunity to say that I have translated, for the same publishers, Professor Guenther's "Darwinism and the Problems of Life," which will shortly be in their hands. JOSEPH MCCABE. _November, 1905._ PREFACE