stence, 40
on variability of wild geraniums, 79
on variability of common species, 80
his non-recognition of extreme variability of wild species, 82
on races of domestic pigeon, 90
on constitutional variation in plants, 95
on unconscious selection, 96
on a case of divergence, 105
on advantage of diversification of structure in inhabitants
of one region, 110
on species of plants in turf, 110
on isolation, 119
on origin of mammary glands, 129
on eyes of flatfish, 129
on origin of the eye, 130
on useless characters, 131
on use of ears and tails, 136
on disappearance of sports, 140
on tendency to vary in one direction, 141
on rare perpetuation of sports, 142
on utility of specific characters, 142 (note)
on importance of biological environment, 148
on variable fertility of plants, 155
on fertile hybrids among plants, 164

Darwin, on correlation of sterility and colour, 169
on selective association, 172
on infertility and natural selection, 174
on cause of infertility of hybrids, 185
on white tail of rabbit, 218
on conspicuous caterpillars, 236
on sexual selection in insects, 274
on decorative plumage of male birds, 285
on development of ocelli, 290
on value of cross-fertilisation, 309
on limits to utility of intercrossing, 326
on flowers due to insects, 332
on oceanic islands, 342
on effects of disuse in domestic animals, 415, 435
on direct action of environment, 419
on unintelligibility of theory of retardation and acceleration,
421 (note)
on origin of man's moral nature, 461
Mr. George, on intermarriages of British aristocracy, 326

Darwinian theory, statement of, 10
not opposed to spiritual nature of man, 478
Dawkins, Professor Boyd, on development of deer's horns, 389
on recent origin of man, 456
Dawson, Sir W., on determination of fossil plants by leaves, 398 (note)

Death of wild animals usually painless, 38

De Candolle, definition of species, 1
on difficulty of naturalising plants, 15
on war between plants, 16
on origin of useful cultivated plants, 97

Deer's horns, development of, 389

Degeneration, 121

Delboeuf's law of variation, 141

Dendraeca coronata, variation of wing-feathers of, 51

Denmark, struggle between trees in, 20

Denudation, evidences of, 379

Desert animals, colour of, 192

Deserts, effect of goats and camels in destroying vegetation in, 17

Development and d