Psychology, comparative, 198; principle of, 199; descriptive, genetic, 202; terms of, 203; human, 210, 211. Pseudopodia, 52. Puma, 101. Pupa, 259. Pygmy, 195, 196, 227. Rabbits, 41, 101; domesticated, 137; introduced into Australia, 140. Races, human, age of, 178; divisions of, 183-195; character of: status, variations of, 180, 181; color, a criterion of racial relationship, 181, 184; hair, character of, as means of classification, 181, 182; cranium, shape of, as means of identification, nose, jaws, 182. Racoon, 38. Rats, 41, 134. Reason, 203; in mental life of communal insects, 207. Religions, 288; Christian, Hebrew, Buddhistic, Tangaroan, 289, 290; Mohammedan, 290, 298; Dervish, Mahdist, 293; linguistic basis of, 293, 294; of savagery, 294, 300, 301; barbarism, civilization, 294; elements of, 295; forms of Christianity, 296; sects, Judaism, 297, 298; Brahmanism, Buddhism, 298, 299; Polytheism, Roman, 300. Reptiles, variations about a central theme, 45; lizard, typical, 46; 157; embryos of, 171; 200. Retention of better invention, 109. Rhinoceros, 41. Rivers, Mississippi, 86, 89; Hoang-ho, Ganges, Thames, 87; alterations made by, 87. Rocks, crystalline or plutonic: sedimentary, 85; eruptive, 88; new, 59; of Grand Canon, 90; testimony of, establishes evolution, 100. Salamanders, 45, 46. Salts, of sodium, chlorine, magnesium, potassium, 24. Samoan Islands, 103. Sandstone, 90. Science, what is it? 5, 6; physiological, 14. Sea anemones, 68. Sea elephant, 38. Seals, 38, 39, 40, 209. Selection, natural, doctrine of, 116, 117, 118; struggle for existence, 124, 125; simply trial and error, 131, 136, artificial, 136, 137, 138; laws of, in mental phenomena, 203. Sequence, physiological, in training animals, 209; 210. Series, sedimentary, 84, 90, 92; crystalline or plutonic, 85; Azoic or Archaean, age of, 92. Shale, 89. Shark, common, most fundamental form, 46; embryo of, hammerhead; embryos of, 66. Sheep, 157. Simiidae, 160, 163. Skate, embryos of, 66. Snails, 45; shells of, 95; land snails, 103; Hawaiian and Polynesian, 104. Society Islands, 103. Solar system, origin of, 84. Solomon Islands, 103. Species, origin of human, 153. Spencer, Herbert, 8. Squirrels, evolved from terrestrial rodents, 14; 41; flying, true rodents, 41. Starch, 24. Stephenson, 10. Strata, 88, 89; arranged according to ages, 89; 90; time of formation, 92. Struggle for existence, 124; intra-specific, 125; three divisions of, 126-129; 139, 174, 175. Substances, inorganic, 29. Sugar, 23, 24. Survival of the fittest, 129. Systems, respiratory, excretory, circulatory, 17; organic, reproductive, 18; nervous, 256, 257; blood-vascular, respiratory and excretory, 257; ethical, 286; religious, 288. Tadpole, 58, 59, 60; larvae, 64. Tapeworm, a relative of simple worms, 50; 123.