IV. THE ORIGIN OF PLANT LIFE ON THE LAND 89 V. THE APPEARANCE OF VERTEBRATE ANIMALS 117 VI. THE FIRST AIR-BREATHERS 137 VII. THE EMPIRE OF THE GREAT REPTILES 165 VIII. THE FIRST FORESTS OF MODERN TYPE 185 IX. THE REIGN OF MAMMALS 207 X. THE ADVENT OF MAN 233 XI. REVIEW OF THE HISTORY OF LIFE 253 LIST OF ILLUSTRATIONS. FRONTISPIECE.—Life in the Silurian Age _To face Title._ FIG. PAGE 1. Bank of stream or coast, showing stratification 4 2. Section at Niagara Falls 4 3. Section obtained by boring, near Goderich, Ontario 5 4. Inclined beds, holding fossil plants 6 5. Ideal section of the Apalachian Mountains 7 6. Generalised section across England from Menai Straits to the Valley of the Thames 9 7. Generalised section from the Laurentian of Canada to the coal-field of Michigan 9 8. Unconformable superposition of Devonian Conglomerate on Silurian slates, at St. Abb’s Head, Berwickshire 10 9. Section of Trenton limestone, Montreal 14 10. Diagram showing different state of fossilisation of a cell of a Tabulate Coral 15 11. Cast of erect tree (_Sigillaria_) in Sandstone 16 12. _Protichnites septem-notatus_ 17 12_a_. Footprints of modern _Limulus_, or king-crab 18 13. Current markings on shale, resembling a fossil plant 18 _Frontispiece._ Magnified and restored section of a portion of _Eozoon canadense_ 20 14. Ideal section, showing the relations of the Laurentian and Huronian 24 15. Small weathered specimen of _Eozoon_ 28 16. Nature-printed specimen of _Eozoon_ slightly etched with acid 29 17. Magnified group of canals in supplemental skeleton of _Eozoon_ 31 18. Portion of _Eozoon_ magnified 100 diameters 31 19. Magnified portion of shell of _Calcarina_ 32 20. _Amœba_, a fresh-water naked Rhizopod; and _Actinophrys_, a fresh-water Protozoon 34 21. _Nonionina_, a modern marine Foraminifer 34 22. _Stromatopora concentrica_ 35