456 



STRATA. 



INDEX. 



UTILITY. 



Strata, thickness of, in Britain, 268, 



269. 

 Stripes on horses, 128. 

 Structure, degrees of utility of, 159. 

 Struggle for existence, 48. 

 Succession, geological, 290. 



of types in same areas, 310. 



Swallow, one species supplanting 



another, 59, 

 Swaysland, Mr., on earth adhering to 



the feet of migratory birds, 328. 

 Swifts, nests of, 228. 

 Swim-bladder, 148. 

 Switzerland, lake habitations of, 13. 

 System, natural, 364. 



T. 



Tail of giraffe, 157. 



— — of aquatic animals, 157. 



, prehensile, 188. 



, rudimentary, 400. 



Tanais, dimorphic, 36. 



Tarsi, deficient, 108. 



Tausch, Dr., on umbelliferae, 173. 



Teeth and hair correlated, 115. 



rudimentary, in embryonic, 



on cells of bees. 



calf, 397, 420. 

 Tegetmeier, Mr., 



222, 226. 

 Temminck, on distribution aiding 



classification, 369. 

 Tendrils, their development, 196. 

 Thompson, Sir W., on the age of the 



habitable world, 286. 

 , on the consolidation of the 



crust of the earth, 409. 

 Thouin, on grafts, 246. 

 Thrush, aquatic species of, 142. 



, mocking, of the Galapagos, 356. 



, young of, spotted, 388. 



, nest of, 234. 



Thuret, M., on crossed fuci, 243. 

 Thwaites, Mr., on acclimatisation, 



112. 

 Thylacinus, 374. 

 Tierra del Fuego, dogs of, 211. 



, plants of, 341. 



Timber-drift, 326. 

 Time, lapse of, 266. 



by itself not causing modifica- 

 tion, 81. 

 Titmouse, 141. 



Toads on islands, 350. 



Tobacco, crossed varieties of, 258. 



Tomes, Mr., on the distribution of 

 bats, 351. 



Transitions in varieties rare, 134. 



Traquair, Dr., on flat-fish, 188. 



Trautschold, on intermediate varie- 

 ties, 275. 



Trees on islands belong to peculiar 

 orders, 350. 



with separated sexes, 78. 



Trifolium pratense, 57, 75. 



incarnatum, 75. 



Trigonia, 296. 



Trilobites, 286. 



, sudden extinction of, 297. 



Trimen, Mr., on imitating-insects, 

 377. 



Trimorphism in plants, 35, 252. 



Troglodytes, 234. 



Tuco-tuco, blind, 110. 



Tumbler pigeons, habits of, heredi- 

 tary, 210. 



, young of, 392. 



Turkey-cock, tuft of hair on breast, 

 70. 



, naked skin on head, 158. 



, young of, instinctively wild, 



265. 



Turnip and cabbage, analogous vari- 

 ations of, 125. 



Type, unity of, 166, 167. 



Types, succession of, in same areas, 

 310. 



Typotherium, 302. 



U. 



Udders enlarged by use, 8. 



, rudimentary, 397. 



Ulex, young leaves of, 388. 

 Umbelliferae, flowers and seeds of, 



116. 



, outer and inner florets of, 173. 



Unity of type, 166, 167. 



Uria lacrymans, 72. 



Use, effects of, under domestication, 



8. 



, effects of, in a state of nature, 



108. 

 Utility, how far important in the 



construction of each part, 159. 



