Huxley on Ichthyopsida and Sauropsida, 129. Hyæna, in glacial times of England, 342; teeth and claws of the, 290. Ice, covering Northern Europe, 342. Ichneumon, killing the cobra, 121; _the Egyptian_, 281. Ichthyodorulites of the Silurian, 38. Ichthyopsida, fish and amphibia, 129. Ichthyornis, 130; _figured_, 123. _Ichthyosaurus_, 89, 92. Iguanas or tree-lizards, 106. _Iguanodon_, 89, 93. Imperfect-toothed animals, or Edentata, early history of, 201. _Insect-eater, skull and teeth of_, 217. _Insect-eaters, a group of_, 220; small-sized animals, 215; and rodents compared, 239; absent from South America, 230. Instincts, interest of in theory of development, 347. Invertebrata and their limits, 4–6, 9. Isinglass from sturgeon, 32. Jacamars of America, 168. Jackals, hunting in packs, 285; ancestors of the dog, 286. Jaguar, feeding on tortoise, 100; habits and range of the, 292; and ant-bear, 205. Japan, gigantic salamander of, 78; monkeys in, 241. Jaw, movement of, in flesh-feeders, 289; in vegetable-feeders, 259; _of snake_, 119; distensible, 114. Jerboas of Africa, 225. Jumping shrews, 225. Kangaroo-rats, 195. _Kangaroos_, 193; strength of, 194. Kentucky caves, blind fish of, 68. _Kaola, or native bear of Australia_, 193, 195. Killer-whale, voracity of the, 325. _Kingfisher_, 166; a darting bird, 167. “King of the Herrings,” 41. Knob, on bird’s beak for shell-breaking, 143; on nose of baby platypus, 190. Labyrinthodonts, age of, 337; of the coal-forests, 84. Lakes, fish-eggs carried to, 66. Lamprey, _and young_, 16; breathing organ of, 17; teeth of, 17, 19, 37; metamorphosis of the, 19. Lampris luna, sun-fish, 53. _Lancelet, structure of the_, 11. Land-birds, their enemies and difficulties, 154–156. Lark, nest of the, 170. Legs, of a bird, construction of, 127; vestiges of, in snakes, 110. Leidy cited, 212. Lemming, strange migrations of, 225. _Lemurs_, 244; position and habits of, 243. Lepidosteus or bony pike, 33. Life, gradual development of, 4. Light-giving deep-sea fishes, 47. Lion fighting with a buffalo, 274; formerly in England, 291; habits and range of the, 291. Lizard, _skeleton of a_, 103; structure and habits of, 104; can live in unhealthy places, 104; flying, 106; legless and snake-like, 107. London, hippopotamus bones under, 263. Lories, the lemurs of India, 243. Love, gradual development of parental, 348–350; a reigning law of life, 353. Lumpsucker clinging to rock, 58. Lungs, of frog, 76; of the snake, 113. Machairodus or sabre-toothed tiger, 291; _figured_, 333. Mackerel going in to spawn, 55. Madagascar, true lemurs of, 243. Magpie’s nest, 170.