Sexual instincts, dominance of, 162 — grades of, 183 — importance of, 27 Sexual selection, definition of, 20 — and human evolution, 38 — in the human race, 32 — instance of working of, 147 Sexual Selection Theory, modification of, 154 Sharp, Dr. David, on stridulating organs, 219 Sheep, scent of, 69 Skull, human, malformation of, 35 Smith Woodward, Dr. A., on factors in evolution, 17 Smynthurus, remarkable courtship of, 26 Snail, hermaphrodite state of, 271 — “love-darts” of, 271 — significance of coloration of, 272 Somato-plasm, nature of, 11 South, Mr., on Oak-eggar moth, 202 Spiders, courtship of, 242 _et seq._ — dread sequel to nuptial rites, 246 — drumming of, 237 — nuptial rites in, 248 — remarkable coloration of, 239 — stridulating organs in, 237 Starling, Prof., on Hormones, 14, 16 State executions v. State pensions, 286 Stickle-back, paternal care in, 181 — remarkable nest of, 181 Stone-flies, degenerate wings in, 234 — nuptial rites performed in ice, 233 Stridulating organs of grass hoppers, 218 — nature of, 217 Sun-bittern, display of, 142 Syrinx in birds, 123 Termite, amazing fertility of queen, 302 “Territory,” importance of, 154 Thomson, Prof. J. A., on evolution of sex, 12, 309 Townsend, Mr., on sea-elephants, 87 Tragopans, display of, 100 Trimen, Dr., on deceptive coloration in a spider, 240 Turkey, display of, 99 Use, inherited effects of, 59 Virgin births, belief in, 296 Voice in birds, 123 Wallace, Alfred Russell, and Sexual Selection, 13, 137, 196 Warblers, play in, 121 Water-fleas, olfactory organs of, 261 Water-fleas, mating apparatus of, 226 Weismann, Professor, on coloration of butterflies, 187 Whales, armature of, 89 — battering-rams of, 179-89 Wheel-animalcule, vitality of, 307 Windpipes, where coiled, 128 Zebras, fighting among, 73 Printed at The Chapel River Press, Kingston, Surrey. ERRATUM For the first line of page 16, instead of “by certain glands of the ductless glands,” read: “by certain of the ductless glands.” End of Project Gutenberg's The Courtship of Animals, by William Plane Pycraft