Artificial selection, analogy of, to natural selection, 295-314; pictorial representations of products of, 298-312. Artiodactyls, 182-191. Association, principle of, in æsthetics, 404-407. Aster, 129-133. Attraction-spheres, 128, 132, 133. Australia, fauna of, 204, 205; thriving of exotic species in, 286; portrait of wild dog of, 304. Azores, 224, 225. B. Bacon, Lord, on scientific method, 2. _Balanoglossus_, 147, 148. _Baptanodon discus_, posterior limb of, 179-181. Barriers, in relation to geographical distribution, 216-224. Bats, 56, 224, 226, 240. Battle, law of, 385, 386. Baya-bird, 381. Bear, skeleton of, 174; feet of, 178. Beautiful, the, sense of, in animals, 380-385; standards of, 380-404; Darwin's explanation of, in organic nature, 379-411; facts of, in inorganic nature in relation to Darwin's theory of, in organic, 404; often determined by natural selection, 406, 407; absent in many plants and animals, 408; in nature often accidental, 409-411; does not exist in organic nature as an end _per se_, 410, 411. Bees, co-operative instincts of, 268. Beetles, wingless, 68-70; on oceanic islands, 224, 226, 229, 232. Bell, Dr., on natural theology, 412. Bell-bird, 396-398. _Bembidium_, 233. Bermudas, 225-227. Biology, ideas of method in, 1-9. Birds, ovum of, 124; embryology of, 151-155; paleontology of, 163-165, 172, 173; brain of, 194-197; as carriers of seed, eggs, and small organisms, 217, 218; distribution of, 224-240; æsthetic sense of, 380-385; courtship of, 380-385. _Birgus latro_, 62-65. Blood, colour of arterial, 409. Boar, _see_ Pig. _Bombus lapidarius_, 331. Bower-birds, play-houses of, 381-383. Boyd-Dawkins, on flattening of early human tibiæ, 96. Brain, palæontology of, 194-197. British Isles, _see_ Islands. Broca, 363. Bronn, 363. Budding, _see_ Germination. Burdon-Sanderson, Prof., on electric organ of skate, 366. Butler, Bishop, on argument from ignorance, 41. Butterflies, defensive colouring of, 321-329. C. Cæsalpino, on classification, 24. Calf, embryology of, 153. Camel, foot of, 187-191. Canadian stag, 196, 198, 199. Canaries, portraits of, 303; first mentioned by Gesner, 312, 313. Cape de Verde Archipelagoes, fauna of, 228. _Carcharias melanopterus_, 149. Carruthers, on evolution, 436-442. Caterpillars, colours and forms of, 319, 322-326. Cattle, portraits of, 311. Causation, natural, 402, 413, 414. Caves, faunas of dark, 70-72. Cell, physiological, and properties of the, 104-134. _Cerura vinula_, 325, 326. _Cervalces Americanus_, 196, 198, 199. _Cervus dicrocerus_, _issiodorensis_, _matheronis_, _pardinensis_, _Sedgwickii_, _tetraceros_, 168. Chalmers, Dr., on natural theology, 412. Chameleons, 317. Characters, as adaptive, 273-276, 286-293, 349; as specific, 274-276, 286-295; as congenital and acquired, 274-276. _Chasmorhynchus niveus_, and _C. tricarunculatus_, 396-398.