_n._, 185-189;
--alternating with subsidence, importance of for evolution, 33, 190;
--bad for preservation of fossils, 194

Embryo, branchial arches of, 42, 220;
--absence of special adaptation in, 42, 44 _n._, 220, 228;
--less variable than parent, hence importance of embryology for
classification, 44 _n._, 229;
--alike in all vertebrates, 42, 218;
--occasionally more complicated than adult, 219, 227

Embryology, 42, 218;
its value in classification, 45, 200;
law of inheritance at corresponding ages, 44 _n._, 224;
young of very distinct breeds closely similar, 44 _n._, 225

Ephemera, selection falls on larva, 87 _n._

Epizoa, 219

Essay of 1842, question as to date of, xvi;
description of MS., XX;
compared with the _Origin_, xxii

Essay of 1844, writing of, xvi;
compared with that of 1842 and with the _Origin_, xxii

Evolution, theory of, why do we tend to reject it, 248

Expression, inheritance of, 114

Extinction, 23, 147, 192;
locally sudden, 145;
continuous with rarity, 147, 198

Extinction and rarity, 198

Eye, 111 _n._, 128, 129, 130

Faculty, in relation to instinct, 123

Faunas, alpine, 30, 170, 188;
of Galapagos, 31 _n._, 82, 159;
insular-alpine very peculiar, 188;
insular, 159, 160

Fauna and flora, of islands related to nearest land, 187

Fear of man, inherited, 17, 113

Fertility, interracial, 103, 104

Fish, colours of, 130, 131;
eggs of carried by water-beetle, 169;
flying, 128 _n._;
--transported by whirlwind, 169

Floras, alpine, 162;
of oceanic islands, 162;
alpine, related to surrounding lowlands, 163;
alpine, identity of on distant mountains, 163;
alpine resembling arctic, 164;
arctic relation to alpine, 164

Flower, morphology of, 39, 216;
degenerate under domestication if neglected, 58;
changed by selection, 66

Fly, causing extinction, 149

Flying, evolution of, 16, 131

Food, causing variations, 1, 58, 77, 78

Formation (geological) evidence from Tertiary system, 144;
(geological), groups of species appear suddenly in Secondary, 26, 144;
Palaeozoic, if contemporary with beginning of life, author's theory
false, 138

Formations, most ancient escape denudation in conditions unfavourable to
life, 25, 139

Forms, transitional, 24, 35 _n._, 136, 142, 194;
on rising land, 196