Fossils, Silurian, not those which first existed in the world, 26, 138; falling into or between existing groups and indirectly intermediate, 24, 137; conditions favourable to preservation, not favourable to existence of much life, 25, 139, 141 Fruit, attractive to animals, 130 Galapagos Islands and Darwin's views, xiv; physical character of in relation to fauna, 31 _n._, 159 Galapagos Islands, fauna, 31 _n._, 82 Gasteropods, embryology, 218 Genera, crosses between, 11, 97; wide ranging, has wide ranging species, 155; origin of, 209 Geography, in relation to geology, 31 _n._, 174, 177 Geographical distribution, _see_ Distribution Geology, as producing changed conditions, 4; evidence from, 22, 133; "destroys geography," 31 _n._ Glacial period, effect of on distribution of alpine and arctic plants, 165 Habit in relation to instinct, 17, 113, 115, 116 Habits in animals taught by parent, 18 Heredity, _see_ Inheritance Homology of limbs, 38, 214 Homology, serial, 39, 215 Hybrid, fowls and grouse, 11; fowl and peacock, 97; pheasant and grouse, 97; Azalea and Rhododendron, 97 Hybrids, gradation in sterility of, 11, 72, 97; sterility of not reciprocal, 97; variability of, 78; compared and contrasted with mongrel, 107 Individual, meaning of term, 58 Inheritance of acquired characters, _see_ Character Inheritance, delayed or latent, 43, 44 _n._, 223; of character at a time of life corresponding to that at which it first appeared, 43, 44 _n._, 223; germinal, 44, 222, 223 Insect, adapted to fertilise flowers, 87; feigning death, 123; metamorphosis, 129; variation in larvae, 223 Instinct, variation in, 17, 112; and faculty, 18, 123; guided by reason, 18, 19, 118; migratory, 19; migratory, loss of by woodcocks, 120; migratory, origin of, 125; due to germinal variation rather than habit, 116; requiring education for perfection, 117; characterised by ignorance of end: _e.g._ butterflies laying eggs, 17, 118; butterflies laying eggs on proper plant, 118, 127; instinct, natural selection applicable to, 19, 120 Instinct, for finding the way, 124; periodic, _i.e._ for lapse of time, 124; comb-making of bee, 125; birds feeding young, 19, 126; nest-building, gradation in, 18, 120, 121, 122; instincts, complex, difficulty in believing in their evolution, 20, 121 Intermediate forms, _see_ Forms Island, _see_ Elevation, Fauna, Flora Island, upheaved and gradually colonised, 184 Islands, nurseries of new species, 33, 35 _n._, 185, 189 Isolation, 32, 34 _n._, 64, 95, 183, 184 Lepidosiren, 140 _n._, 212 Limbs, vertebrate, of one type, 38, 216