120;
Woodcock, loss of migratory instinct, 120;
Woodpecker, 6, 16, 128 _n._, 148;
--in treeless lands, 16, 131;
Wood-pigeon, 122;
Wren, gold-crested, 120;
--willow, 105, 148

Breeds, domestic, parentage of, 71

Brothers, death of by same peculiar disease in old age, 42 _n._,
44 _n._, 223

Bud variation, 58;
_see_ Sports

Butterfly, cabbage, 127

Catastrophes, geological, 145, 147

Caterpillars, food, 126, 127

Characters, acquired, inheritance of, 1, 57, 60, 225;
--congenital, 60;
--fixed by breeding, 61;
--mental, variation in, 17, 112, 119;
--running through whole groups, 106;
--useless for classification, 199

Cirripedes, 201, 229

Classification, natural system of, 35, 199, 206, 208;
--by any constant character, 201;
--relation of, to geography, 202;
--a law that members of two distinct groups resemble each other not
specifically but generally, 203, 212;
--of domestic races, 204;
--rarity and extinction in relation to, 210

Compensation, law of, 106

Conditions, direct, action of, 1, 57 _n._, 62, 65;
--change of, analogous to crossing, 15, 77 _n._, 105;
--accumulated effects of, 60, 78;
--affecting reproduction, 1, 4, 78, 99;
--and geographical distribution, 152

Continent originating as archipelago, bearing of on distribution, 189

Cordillera, as channel of migration, 34 _n._, 191

Correlation, 76

Creation, centres of, 168, 192

Crocodile, 146

_Cross-and Self-Fertilisation_, early statement of principles of, 15,
69 _n._, 103 _n._

Crossing, swamping effect of, 2, 69, 96;
--of bisexual animals and hermaphrodite plants, 2;
--analogous to change in conditions, 3, 15, 69;
--in relation to breeds, 68;
--in plants, adaptations for, 70

Death, feigned by insects, 123

Difficulties, on theory of evolution, 15, 121, 128, 134

Disease, hereditary, 43 _n._, 58, 222

Distribution, geographical, 29, 31, 151, 174, 177;
--in space and time, subject to same laws, 155;
--occasional means of (seeds, eggs, &c.), 169

Disuse, inherited effects of, 46, 57

Divergence, principle of, xxv, 37 _n._, 145 _n._, 208 _n._

Domestication, variation under, 57, 62;
--accumulated effects of, 75, 78;
--analysis of effects of, 76, 83

Ears, drooping, 236

Elevation, geological, favouring birth of new species, 32, 34 _n._,
35