Page:Darwinism by Alfred Wallace 1889.djvu/514

 Pelagic animals, colours of, 193

Phasmidae, resemblance of, to sticks and leaves, 203

Physiological selection, 180

Pickard-Cambridge, Rev. O., on sexual selection, 296 (note)

Pieridae, sexual diversity among, 271

Pigeons, varieties of, 89 domestic, derived from wild rock-pigeons, 90 curious correlations in, 140 white eggs of, protective, 213

Pigs, great increase of, in South America and New Zealand, 28

Pikermi, extinct animals of, 377

Pipits as illustrating divergence, 108

Planorbidae, variations of, 44

Plants, the enemies of, 16 variability of, 76 constitutional variation of, 94 colour relations of, 302 true mimicry rare in, 303 exotic rarely naturalised in Europe, 356 dispersal of, 361 northern, in southern hemisphere, 368 identical on summits of remote mountains, 369 progressive development of, 397 geological development of (diagram), 402

Plovers, recognition marks of (figure), 221

Plumes, origin of accessory, 291 muscular relation of ornamental, 292

Poisonous fruits, 307

Porto Santo, rabbits of, 326

Poulton, Mr. E.B., on variable colours of larvae and pupae, 196, 198 on concealments of insects by resemblance to environment, 202 on protective form of Notodonta ziczac, 210 on inedibility of conspicuous larvae, 237

Pouters, 90

Primulaceae, variations of structure in, 79

Problem, the, before Darwin, 6

Problems in variation and heredity, 410

Progression in plants and animals, 395

Protection by terrifying enemies, 209

Protective colouring, variable, 195 of white-headed fruit-pigeon, 200 of African sun-birds, 200 of Kerivoula picta, 201 of sloths, 201 of larva of Sphinx ligustri, 202 of stick and leaf insects, 203 of caterpillars, 203, 205 of butterflies, 206

Ptilopus cinctus, protective colour of, 200

Pugnacity of birds with accessory plumes, 294

R

Rabbit, use of white tail of, 218

Rapid increase of plants, 28

Raspail, M., on variability in a grass, 80

Rat, black, spread of, 34

Rattlesnake, use of rattle of, 262

Raven, why black in arctic regions, 191

Reciprocal crosses, 155

Recognition marks of herbivora, 218 of birds, 222 of tropical forest birds, 224 of insects, 226

Reproductive functions, susceptibility of, 153

Reptiles, geological distribution of, 406

Rhinoceroses, evidence of evolution afforded by fossil, 383

Rocks, all stratified formed in shallow water, 344

Rocky Mountains, scarcity of monocotyledons in, 401

Rodents, prevent woody vegetation in the pampas, 23

Romanes, Professor G.J., on useless characters, 131, 139 on meaningless peculiarities of structure, 140 on supposed absence of simultaneous variations, 142 on physiological selection, 180