In these circumstances it has been thought fitting that we should introduce to English readers the latest work of Professor Haeckel. Germany, as the reader will quickly perceive, is witnessing the same strange reaction of thought that we see about us here in England, yet _Die Welträthsel_ found an immediate and very extensive circle of readers. One of the most prominent zoologists of the century, Professor Haeckel, has a unique claim to pronounce with authority, from the scientific side, on what is known as "the conflict of science and religion." In the contradictory estimates that are urged on us--for the modern ecclesiastic is as emphatic in his assurance that the conflict has ended favorably to theology as the rationalist is with his counter-assertion--the last words of one of the leading combatants of the second half of the century, still, happily, in full vigor of mind, will be heard with respect and close attention. A glance at the index of the work suffices to indicate its comprehensive character. The judgment of the distinguished scientist cannot fail to have weight on all the topics included; yet the reader will soon discover a vein of exceptionally interesting thought in the chapters on evolution. The evolution of the human body is no longer a matter of serious dispute. It has passed the first two tribunals--those of theology and of an _à priori_ philosophy--and is only challenged at the third and last--that of empirical proof--by the decorative heads of scientific bodies and a few isolated thinkers. "_Apparent rari nantes in gurgite vasto._" But the question of the evolution of the human mind, or soul, has been successfully divorced from that of the body. Roman Catholic advanced theologians, whose precise terminology demanded a clear position, admit the latter and deny the former categorically. Other theologians, and many philosophers, have still a vague notion that the evidence for the one does not impair their sentimental objection to the other. Dr. Haeckel's work summarizes the evidence for the evolution of mind in a masterly and profoundly interesting fashion. It seems impossible to follow his broad survey of the psychic world, from protist to man, without bearing away a conviction of the natural origin of every power and content of the human soul. TRANSLATOR. _October, 1900._ THE RIDDLE OF THE UNIVERSE CHAPTER I THE NATURE OF THE PROBLEM