Selection, mechanical, 410. Semper, C., 406. Series, animal, branching, 235, 264, 282. Serpents, origin of, 290, 309; eyes of, 314. Sexual selection, 219, 224. Shell, bivalve, origin of, 418; crustacean, 418. Shells, deep-water, 112; fossil, 40, 120, 125, 131; Lamarckian genera, 183. Simia satyrus, 367; troglodytes, 364. Sloth, 320. Snakes, atrophy of legs of, 290, 309; eyes of, 314; origin of, 290, 309; tongue of, 313. Sole, 314. Species, Buffon's views on, 201, 221; definition of, 252, 255, 262, 267, 275; extinct, 126; Geoffroy St. Hilaire, views on, 214; Lamarck's views on, 183; modification of, 131; origin of, 131, 283; stability of, 271, 277, 401; variation in, 278. Speech, 370. Spencer, Herbert, 371, 382, 384, 415. Spermist, 218. Sphalax, 307. Spines, 251, 393, 414. Sponges, 194. Squirrel, flying, 338, 339. Stimulus, external, 348, 354, 393. Struggle for existence, 207, 237, 287. Surroundings, 214, 421; local, 410. Symmetry, radial, 291. Swan, 313. Tail, of kangaroo, 318. Teeth, 307; atrophy of, 307; in embryo birds, 307; in whales, 307. Temperature, 410. Tentacles of snail, 348, 354. Tertiary shells, 110, 125, 133. Thought, definition of, 172. Time, geological, 119, 130, 222, 236. Toes, modifications of, 234, 311, 315, 317, 321, 338, 344. Tree, genealogical, first, 130, 181, 192, 193, 349. Trout, 403. Tubercles, origin of, 394. Tunicata, position of, 195. Turbot, 314. Turtle, sea, 312. Uniformitarianism, 130. Use, 248, 256, 257, 302, 303, 311, 318, 384, 412. Use-inheritance, 219, 224, 246, 276, 303, 319, 346. Use originates organs, 276, 311, 346. Variability, 407. Variation, climatic, 204, 218, 401; causes of, 218, 266. Varieties, 401. Varigny, H. de, 408. Vestigial organs, 307, 308. Vital force, 167. Vitalism, 168. Volucella, 338. Wagner, M., 404. Wallace, A. R., on origin of giraffe's neck, 351. Wants, 245, 270, 274, 281, 295, 302, 324, 334, 346, 350, 351, 352. Ward, L. F., 422. Water, diversified condition of, 290. Werner, 97. Whale, 307, 343, 409. Will, 319, 330, 337. Willing, 236, 351, 412. Weismann, A., 399. Wings, atrophy of, in insects, 309. Woodpecker, 313. End of the Project Gutenberg EBook of Lamarck, the Founder of Evolution, by Alpheus Spring Packard