Transcriber's Note: Every effort has been made to replicate this text as faithfully as possible, including inconsistencies in hyphenation. It seems that the italic typeface used in this book did not have an ae ligature. Names of genera and higher taxonomic groups are not capitalized in the printed book: they have bee left unchanged. Some changes have been made. They are listed at the end of the text. Italic text has been marked with _underscores_. OE ligatures have been expanded. THE RIDDLE OF THE UNIVERSE [Illustration: ERNST HAECKEL] THE RIDDLE OF THE UNIVERSE _AT THE CLOSE OF THE NINETEENTH CENTURY_ BY ERNST HAECKEL (Ph.D., M.D., LL.D., Sc.D., and Professor at the University of Jena) AUTHOR OF "THE HISTORY OF CREATION" "THE EVOLUTION OF MAN" ETC. TRANSLATED BY JOSEPH McCABE [Illustration] HARPER & BROTHERS PUBLISHERS NEW YORK AND LONDON 1905 Copyright, 1900, by HARPER & BROTHERS. _All rights reserved._ CONTENTS PAGE AUTHOR'S PREFACE v TRANSLATOR'S PREFACE xi CHAPTER I THE NATURE OF THE PROBLEM 1 CHAPTER II OUR BODILY FRAME 22 CHAPTER III OUR LIFE 39 CHAPTER IV OUR EMBRYONIC DEVELOPMENT 53 CHAPTER V THE HISTORY OF OUR SPECIES 71 CHAPTER VI THE NATURE OF THE SOUL 88 CHAPTER VII PSYCHIC GRADATIONS 108 CHAPTER VIII THE EMBRYOLOGY OF THE SOUL 132 CHAPTER IX THE PHYLOGENY OF THE SOUL 148 CHAPTER X CONSCIOUSNESS 170 CHAPTER XI THE IMMORTALITY OF THE SOUL 188 CHAPTER XII THE LAW OF SUBSTANCE 211 CHAPTER XIII THE EVOLUTION OF THE WORLD 233 CHAPTER XIV THE UNITY OF NATURE 254 CHAPTER XV GOD AND THE WORLD 275 CHAPTER XVI KNOWLEDGE AND BELIEF 292 CHAPTER XVII SCIENCE AND CHRISTIANITY 308 CHAPTER XVIII OUR MONISTIC RELIGION 331 CHAPTER XIX OUR MONISTIC ETHICS 347 CHAPTER XX SOLUTION OF THE WORLD-PROBLEMS 365 CONCLUSION 380 INDEX 385 AUTHOR'S PREFACE