how useful, 284
produced by peculiar feathers, 284

South America, fossil and recent mammals of, 393

Species, definition of, 1, 2
origin of, 2, 6
Lyell on, 4
Agassiz on, 5
transmutation of, 6
Geoffroy St. Hilaire on, 6
Dean Herbert on, 6
Professor Grant on, 6
Von Buch on, 6
allied, found in distinct areas, 36

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

Tree