490 
INDEX 
Pelagic animals, colours of, 193 
Phasmidae, resemblance of, to sticks 
and leaves, 203 
Physiological selection, 180 
Pickard-Cambridge, Rev. 0., 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 
Planorbidse, variations of, 44 
Plants, the enemies of, 16 
variabinty 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 hemi¬ 
sphere, 368 
identical on summits of remote 
mountains, 369 
progressive development of, 397 
geological development of (dia¬ 
gram), 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 Noto- 
donta 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 mono¬ 
cotyledons 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 simul¬ 
taneous variations, 142 
on physiological selection, 180 
