ss characters, 131, 139
on meaningless peculiarities of structure, 140
on supposed absence of simultaneous variations, 142
on physiological selection, 180

Rook and crow, 2

Roses, Mr. Baker on varieties of, 77

Rubus, Bentham and Babington on species and varieties of, 77

Rudiments and variations in man, 446

Runts, 91

Rutaceae, variation of structure in, 79

=S=

St. Helena, destruction of forests by goats, 17

St. Hilaire, M. Aug., variability of Gomphia oleaefolia, 79

Saxicola, divergence of character in species of, 108
recognition marks of, 222

Scientific opinion before Darwin, 4

Scolopax, figures of tails of, 225

Scudder, Mr. S.H., on inedibility of Danais archippus, 238
on fossil insects, 403

Seebohm, Mr., on swamping effects of intercrossing, 143

Seeds, how dispersed, 306
how protected, 307
floating great distances, 361
dispersal of, by wind, 362
weight and dimensions of, 364
importance of wind-carriage of, 372
remarkable case of wind-carriage of, 373

Seiurus carolinensis, diagram of variation, 67
sp., habits of, 117

Selection, artificial, 84
by man, circumstances favourable to, 96
unconscious, 96

Selective association, isolation by, 171

Self-fertilisation of flowers, 321

Semper, Professor, on casting hairs of reptiles and Crustacea, 137 (note)
on direct influence of environment, 426

Sesiidae, mimicry by, 240

Sex colour and nests of birds, 277

Sex, colours characteristic of, 269

Sexual colours of insects, probable causes of, 273
of birds, 275
characters due to natural selection, 283
diversity the cause of variation, 439

Sexual selection and colour, 274
by struggles of males, 282
neutralised by natural selection, 294-296
restricted to male struggles, 296

Shetland Islands, variety of ghost-moth in, 270

Shrews and field-mice, internal variations of, 69

Shrikes, recognition marks of, 222

Similarity of forms of life not due to similarity of conditions, 339

Singing of male birds, use of, 284

Skull of wolf, diagram of variations of, 70
of Ursus labiatus, diagram of variations of, 72
of Sus cristatus, diagram of variations of, 73

Skunk an illustration of warning colour, 233

Slack, Baron von, on protective markings of sloths, 201

Sloth, protective colour and marking of, 201

Snakes, mimicry of poisonous, 261

Snipe, tails of two species (figs.), 225

Sounds and odours peculiar to male,