Instinct, determined by heredity, 206; of higher animals, 208; differs from intelligence in degree, 210. Intelligence, 203; in mental life of communal insects, 207. Invertebrates, lower animals devoid of backbone, 47; structural plan, 48; branches of, 49; groups, two layer animals, 50; hydra, sea-anemones, soft-polyps, 50; more complicated, 68; palaeontological materials, 82; evolution of lowest members, 92. Jaguar, 101. Jastrow, 294. Java, 173. Jellyfish, 81. Jordan, David Starr, 123. Kangaroo, 42. Keane, 185. Lamarck, 115, 133, 135. Lampreys, 156. Language, most important single possession of mankind, 218. Laplace, 29. Larvae, of lobster, 66; of insects, 67; of ground wasp, 207; of caterpillar, 259; of wasps, 260. Lavoisier, 29. Law of Recapitulation, 66; stated by Von Baer and Haeckel, 71. Lemurs, 158, 160, 161, 195. Life, what is it? 27. Limestone, 89, 90. Links, 99. Linnaeus, 79, 158, 183. Lions, 101; environment of, 112. Lizard, nearest form to remote ancestor, 45. Lobsters, 66; larvae of, 66. Lyell, 80, 107, 135, 136. MacDougal, 148. Madagascar, 161. Mallock, 295. Malthus, 136. Mammalia, lower orders of, 42; their own mode of growing up, 64; embryos of, 64; 97; members of class differ, 157, 158; 200; order of mentality, 203. Mammals, 40, 43, 157; embryo of, 171. Mammoth, 97. Marmosets, 161. Marquesas, 103. Marsupials, 104. Mastodon, 97. Mechanism, organic, 14; living, 110. Melanesia, 103. Mendel, Gregor, 145; his law, 146; 147, 148. Mentality, human, 233. Metazoa, 254. Mice, 41, 134; field, 139. Miller, 293. Mind, anatomy of, 202; human, differs only in degree, 203; 210, 211; embryology of, 214; palaeontology of, 217; and matter inseparable, 234-237. Missing links, 77. Moeritherium, a significant fossil, 97. Molecule, protein, 22, 23, 24. Mollusks, 81, 82; connecting widely separated ages, 95. Monkeys, 158. Morgan, Lloyd, 148. Morphology, 32. Moths, 67. Mueller, 293. Mutation theory, 146. Naegeli, 143, 148. Natural Selection, doctrine of, 116, 117, 118; the struggle for existence, 124, 125; simply trial and error, 131; Darwin recognized it as incomplete, 142; germ-plasm theory supplements, 145. Nebula, gaseous, 84. Nervous systems, 201, 202, 205, 206, 211; of worker-bee, 232. Niagara, 85, 86, 89. Ontogeny, recapitulates phylogeny, 63. Orang-outang, 163, 164. Orders, 32. Organic, 15; systems, 17; transformation, analogies of, 43, a real and natural process, 55, 56, 76; mechanism, alteration of, 55.