470 
Silver-bill, 410, 
Sirex, 181. 
Siricidze, 181. 
Sitaria, 194. 
Skin, thickening of, 12, 13. 
Skull, 37, 65. 
Skunk, 3. 
Slaves of ants, 141. 
Sleep in plants, 404. 
Sloth, 229. 
Snail, 417. 
Snails, color of, 23. 
Snakes, 14, 193-194, 227. 
Snowy owl, 6. 
Solenobia, 419. 
Soles, 137, 228. 
Sparassus, 178. 
Sparrow, 200; English, 112. 
Species, 31, 32, 33; adaptation for good of, 
1g; sharp separation of, 131. 
Spencer, 240-246, 247, 290. 
Spermatozoa, 150, 430-433. 
Sphinx, 186, 388. 
Spiders, 177-178, 179, 406; web, 3. 
Spirogyra, 420. 
Spontaneous variability, 134. 
Spores, 322. 
Squilla, 177. 
Squirrels, 210. 
Stag-beetle, 179. 
Stags, 203-204, 219. 
Sterility, 147-152. 
Strasburger, 395. 
Stridulating organs, 188, 189. 
Struggle for existence, Iog, IIo, 
Stylonychia, 442. 
Survival of the fittest, 107, 108, 109, 117. 
Sutton, 432. 
Swallow, 115. 
Sweating, 12, 
Tadpole, 321, 428. 
Tail, a 
Tanager, 6. 
Tapeworm, 353; number of eggs, 110, 
Taraxacum, 305. 
Tear-sacs, 206. 
Teeth, bird's, 67, 68. 
Telegony, 95, 234, 237, 238, 239. 
Tenthredinidee, 181, 425. 
Termite, number of eggs, 110. 
Termitidze, 350. 
Thrush, 115. 
Tipule, 188. 
Toad, 7. 
Torpedo, 132, 
Towle, 392. 
Lndex 
Transitional forms, 42, 
Transmutation theory, 31,.34- 
Traquair, 138. 
Treadwell, 72. 
Treat, 424. 
Tree-frogs, 7. 
Trichina, 353. 
Trifolium, 404, 
_| Triton, 193. 
Turkeys, 314. 
Turnix, 201, 202, 
Turtles, 193. 
Umbelliferze, 135. 
Uria lacrymans, 124. 
Utricularia, Io. 
Vanessa, 360. 
‘Variability, 92, 93, 95, 96, 318-319. 
Variation, 261, 340. 
Variation, fluctuating, 100, 118, 123. 
Variation under domestication, 136. 
Varieties, 106, 107, 148. 
Varigny, De, 303-306, 314-315, 322. 
Venus fly-trap, 9. 
Verbascum, 148, 149. 
Vertebrates, evolution of, 40, 45. 
Vilmorin, 303, 314. 
Vinson, 178. 
Vries, De, 97, 278, 289-298, 340. 
Vulpine, 209. : 
Wallace, 7, 162, 186, 202, 221, 249, 
Walrus, 203. 
Walsh, 181. 
Walther, 59. 
Wasp, 3, 5, 408, 409. 
Waterton, 198. 
Web, spider's, 3, 4. 
Weir, 171. 
Weismann, 154-166, 441, 448-450. 
Westwood, 188. 
Whale, 227, 301. 
Wilson, E. B., 72. 
Wing of bat, 2. 
Wolf, 308, 376. 
Wolves, 412. 
Women, 210. 
Woodpecker, 228, 
Wounds, healing of, 15. 
Yarrell, 138. 
Yung, 424, 436. 
Zebu cattle, 208, 
Zeleny, 348. 
Zoéa, 69, 70, 
