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492 Species, which vary little, 80 closely allied inhabit distinct areas, 111 vigour and fertility of, how kept up, 327

Spencer, Mr. Herbert, on factors of organic evolution, 411 on effects of disuse, 413 on difficulty as to co-adaptation of parts, 417 on direct action of environment, 418

Sphingidae, protective attitudes of larvae, 210

Sphinx ligustri, general resemblance of larva to food plant, 202

Spider, alluring coloration of, 211

Spines, on origin of, 431 rarity of, in oceanic islands, 432

Spiny plants abundant in South Africa and Chile, 433

Spots a primitive ornamentation of animals, 289

Sprengel on flowers and insects, 309

Staphylinidae, protective habit of, 210

Sterility of mongrels, 165 correlated with colour, etc., 168 and natural selection, 173 of hybrids produced by natural selection, 179

Struggle for existence, 14 among plants, 15 for life, illustrations of, 18 for existence on the pampas, 22 for life between closely allied forms most severe, 33 for existence, ethics of, 36 how it acts among flowers, 328

Summary of facts of colouring for protection and recognition, 227

Survival of the fittest, 11, 122, 123

Swainson, definition of species, 2

Swamping effects of intercrossing, 142

Sweden, destruction of grass by larvae of moths in, 17

Swinhoe, Mr., on protective colouring of a bat, 201

Symmetry, bilateral in colours of animals needful for recognition, 217

T

Tails used as respirators, 136

Tapirs, distribution of, 352

Tegetmeier, Mr., on feeding habits of pigeons and fowls, 75 on sparrows and crocuses, 75 on curious correlations in pigeons, 140

Tegumentary appendages and colour, 291

Thousand-fathom line divides oceanic from continental islands, 347 the teachings of, 348 map showing, 349

Thwaites, Mr., on spread of Lantana mixta in Ceylon, 30

Tiger, use of stripes of, 199

Titmice as illustrating divergence, 107

Transformation of species of crustacea, 427

Transmutationists, the early, 3

Travers, Mr. W.L., on effects of introduced plants in New Zealand, 29

Trees, great variety of, in many forests, 36

Trimen, Mr., on butterfly deceived by its mimic, 245 on mimicry, 247

Tropical animals, why brilliantly coloured, 299

Tropics, no proof of lower temperature of, 369

Tropidorhynchi mimicked by orioles, 263

Trumpeter, 93

Tumblers, 91

Turbits and owls, 91

Tylor, Mr. A., on Coloration in Animals and Plants, 285

U

Ungulates, origin of feet of, 423

Use and disuse, effects of, overpowered by natural selection, 435

Useless characters, 131 not specific, 132