UNSTABLE ENVIRONMENT 81 Development of North America 85 Archæan Era 85 Palæozoic Era 86 Silurian Period 87 Devonian Period 87 Carboniferous Period 87 Jurassic Period 88 Cretaceous Period 88 Tertiary Period 89 Quaternary Period 89 SECTION IV. TRANSMUTATIONS OF LIVING FORMS 93 Archæan Era 94 Table of Stratified Rocks and the Successive Appearance of Typical Life-Forms 95 Cambrian Period 96 Lower Silurian Period 96 Upper Silurian Period 98 Devonian Period 100 Carboniferous Period 102 Permian Period 104 Triassic Period 105 Jurassic Period 106 Cretaceous Period 108 Tertiary Period 110 Quaternary Period 113 SECTION V. NATURAL SELECTION 119 Artificial Selection 120 Multiplication of Animals 122 Elimination of the Unfit 125 The Coloration of Animals and Environment 127 Protective Coloration 128 Protective Resemblance 138 Alluring Coloration 141 Warning Coloration 144 Mimicry 147 Recognition Marks 150 Sexual Selection 152 Insect Selection 160 Isolation of Varieties 166 SECTION VI. EVOLUTION OF MAN 173 Development of the Frog 173 Development of Man 180 Useless Scaffolding in Man 191 Development of the Brain 199 The Brain and Psychic Phenomena 206 Evolution and Social Problems 222