Page:Darwinism by Alfred Wallace 1889.djvu/510

 Horse tribe, pedigree of, 384 ancestral forms of, 386

Humming-birds, recognition marks of, 226

Huth, Mr., on close interbreeding, 160

Huxley, Professor on the struggle for existence, 37 on fossil crocodiles, 383 on anatomical peculiarities of the horse tribe, 384 on development of vertebrates, 448 on early man, 456 on brains of man and the gorilla, 457

Hybridity, remarks on facts of, 166 summary on, 184

Hybrids, infertility of, supposed test of distinct species, 152 fertility of, 159 fertile among animals, 162 between sheep and goat, 162 fertile between distinct species of moths, 163 fertile among plants, 163

Hymenopus bicornis, resembling flower, 212

I

Icterus Baltimore, diagram showing proportionate numbers which vary, 63

Imitative resemblances, how produced, 205

Increase of organisms in a geometrical ratio, 25

Inedible fruits rarely coloured, 308

Insect and self-fertilisation, alternation of, in flowers, 328

Insect-fertilisation, facts relating to, 316

Insects, coloured for recognition, 226 warning colours of, 233 sexual coloration of, 269 importance of dull colours to female, 272 visiting one kind of flower at a time, 318 and flowers, the most brilliant not found together, 335

Insects, no proof of love of colour by, 336 and birds at sea, 357 in mid-ocean, 359 at great altitudes, 360 geological distribution of, 403 ancestral in Silurian, 405 fossil support evolution, 405

Instability of useless characters, 138

Instinct, the theory of, 441

Insular organisms illustrate powers of dispersal, 354

Interbreeding, close, injurious effects of, 160 supposed evil results of close, 326

Intercrossing, swamping effects of, 142 not necessarily useful, 325

Intermediate forms, why not found, 380

Islands, all oceanic are volcanic or coralline, 342

Isle of Man, small butterflies of, 106

Isolation, the importance of, 119 to prevent intercrossing, 144 by variations of habits, etc., 145 Rev. J.G. Gulick on, 147 when ineffective, 150

Ituna Ilione and Thyridia megisto, figures of wings of, 251

J

Jacobin, 93

Jenyns, Rev. L., on internal variations of mammalia, 69

Jordan, Mons. A., on varieties of Draba verna, 77

Judd, Professor, on dust fallen at Genoa, 363 on Hungarian fossil lacustrine shells, 381

K

Kerguelen Island, wingless insects of, 106

Kerivoula picta, protective colour of, 201