Horses, absence from American continent in fifteenth century of living asses, zebras, and, 89 ancestral, change in size and proportions of, 84, 85 lower Tertiary Hyracotherium, 84 middle Tertiary, 84 “pre-orbital cup” in Hipparion, 85, 86 upper Tertiary Hipparion, 84-86 ancestry of, scientific points of interest with regard to, 83-90 descent from Arab ancestry evidenced by presence of “pre-orbital cup” in, 86 English thoroughbred, history and ancestors of, 82, 90 “Ergot” of, 89 European, stock from which derived, 77-78 fossil remains of extinct, in North and South America, 89, 90 mark of difference between asses, zebras, and, 87, 88 mastery and muzzling of, by ancient cave-dwellers, 80, 81 Mongolian wild, absence of “pre-orbital cup” in, 86 derivation of European horses from, 77-78 description of, 78 prehistoric European, verified by ancient carvings found in caves, 79-81 selective breeding of, from time of cave-men onward, 82, 83 Southern or Arabian breeds of, presence of “pre-orbital cup” in, 86, 87 House-sparrows, 266 Huxley, Professor, calculation of, with regard to fecundity of plant-lice, 338 Hydra, heraldic, derivation of, 116 Hyracotherium horse, 84 India, practice of opium eating in, 366 Infants, blindness of, congenital, 272 mortality of, varied congenital defects causing, 272 Insects, association of, with plants, 296 colour-protection and invisibility of, 304-312 destructive invasions made by various, 339-345 jumping bean as exemplifying association of plants and, 297, 298-300, 302 parthenogenetic powers possessed by certain, 331, 332 poisonous, methods of self-protection used by, 101, 102 various weapons of, 111 “silver-fish,” depredations of, 351 skin burrowing, 112, 113 wood-boring, 346-354 Jelly-fishes, common, description of, 58 fresh-water, discovery of African, 61, 62 Chinese, 63 Philadelphian, 63, 64 Regent’s Park, 59, 60 reproduction of, 60, 61 poison-bearing threads of sea-anemones and, 110 Jumping bean, Mexican, caterpillar contained in, 229, 300, 302 movements of, 298, 299, 302 plant from which derived, 301, 302 relationship of insect and plant exemplified in, 297, 298-300, 302 Kew Gardens, beauty and interest of, 302, 303 specimens of _Rhus toxicodendron_ at, 93, 94 Koch (Berlin), cholera-bacillus discovered by, 240 tubercle-bacillus discovered by, 240 Ladybird, 325 Lamarck, inferiority of scientific methods, as compared with Darwin, 19-22, 26 _Philosophical Zoology_ by, 20 Lankester, Sir Ray, address by, Darwin Centenary Celebration at Cambridge, 33-37 Leprosy, bacillus of, discovery by Hansen, 240 “Leptocephali,” discovery of, 70-72 Life, protoplasm the seat of, 182-184, 328 Herbert Spencer’s definition of, 183, 184 Light, rate at which it travels, 221 Locusts, winged serpents and, probable connection between, 124-125