Scientific questions, decided by evidence, not by authority, 344 Scotland, 107 Sea-anemone, 261 Sea floor, 113 Sea-urchin, 119, 140; egg of, 140 Second causes, 52, 71; efficacy finite, 71 Sediment, 93, 103, 125; primordial, 125; universal layer of, 103 Seedlings, 161 Segregation, 25 Selection, 11, 12, 13, 65, 152, 153, 306; artificial, 152 —not on a par with natural selection, 152; intelligent and fortuitous, 152, 153; principle, 11, 12, 13, 65; values, 306 Self, 205 Self-fertilization, 159 Self-observation, 224, 225; impossible for an organ, 226; power of, cannot reside in material organ, 224, 225; requires a spiritual principle, 225 Self-regulation, 174, 176, 179 Self-sacrifice, rendered meaningless, 356 Semilunar fold, 296, 297 Senescence, 26, 157, 160, 162; an inherent tendency of living matter, 160; tendency practically if not actually universal, 162 Sensationists, 218 Sensations, 209, 227, 242; intensity of, 227 Sense, 204, 227, 228, 235, 254, 350; debilitated by powerful stimulus, 227; external, 204; organic nature of, 227; their power of reaction temporarily inhibited by process of repair, 227, 228 Sense organs, 213, 251 Sense-perception, 199, 203, 214, 219, 220, 227, 231, 235; a brain function 199; a psycho-organic function, 214; concerned with factual reality of existence, 219; involves a decomposition of neural tissue, 227; not independent of body, 227; organic function, 203 Sensibility, organic, 244, 245 Sensori-motor, 251 Sensory functions of the nervous system, 199 Sensual appetites, exhaustible, 232 Sensual emotion, organic function, 203 Sequence, 100, 107, 108; inverted or “wrong,” 107, 108; no invariable order of, 100; of fossiliferous strata, 100; “wrong,” 107, 107 _note_ Serum, 15 Sexual (gametic) incompatibility, 4, 5, 19, 20, 21 Sharks, 80, 119, 296 “Shell-craters,” 347 Shoots, 160 Sight, 217; intrinsic dependence on eye, 217; extrinsic dependence on object, 217 Silurian, 92, 106, 111, 118; Middle, 92, 106 Simia satyrus, 32 Simple explanations not necessarily true, 350 Siwalik beds, 95, 310 Skeleton, 60, 61, 331; human, 331 Skulls, 328, 329, 331, 333, 340, 341; fossil, 33, 341; human, 331 Skull cap, 271, 313, 314, 324, 328 Sleep, would interrupt process of relaying consciousness from thought to thought, 212, 213 Sloth, 52 Snapdragon, 88 Social inequalities, artificial laws for benefit of rich, 361 Socialism, 357, 360; Marxian, 357; Scientific, 357 Sodium, 165, 166; bromide, 165; chloride, 165, 166; iodide, 165