lADEX 



353 



Species, polymorphic, i. tt 



, dominant, i. 90 



, common, variable, i. 89 



iu large genera variable, i. 92 



, groups of, suddenly appearing, 



ii. 83-88 



beneath Silurian formations, ii. 



90 



successively appearing, ii. 96 



——changing simultaneously through- 

 out the world, ii. 108 



Spencer, Lord, on increase in size of 

 cattle, i. 64 



, Herbert, Mr., on the first steps 



in differentiation, i. 181 



, on the tendency to an equilib- 

 rium in all forces, ii. 34 



Sphex, parasitic, i. 363 



Spiders, development of, ii. 254 



Sports in plants, i. 35 



Sprengel, C. C, on crossing, i. 142 



, on ray-florets, i. 206 



Squalodon, ii. 115 



Squirrels, gradations in structure, L 

 242 



Staffordshire, heath, changes in, i. 110 



Stag-beetles, fighting, L 132 



Starfishes, eyes of, i. 251 



, their pedicellarise, i. 326 



Sterility from changed conditioQS of 

 life, i. 34 



of hybrids, ii. 9 



— , laws of, ii. 17 



, causes of, fl. 26 



, from unfavorable conditions, ii. 



32 



not induced through natural se- 

 lection, ii. 27 



St. Helena, productions of, ii. 187 



St. Hilaire, Aug. , on variability of cer- 

 tain plants, i. 298 



, on classification, ii. 218 



St. John, Mr., on habits of cats, i. 363 



Sting of bee, i. 282 



Stocks, aboriginal, of domestic ani- 

 mals, i. 45-46 



Strata, thicliness of, in Britain, ii. 61 



Stripes on horses, i. 225 



Structure, degrees of utility of, i. 275 



Struggle for existence, i. 98 



Succession, geological, ii. 96 



of types in same areas, ii. 128 



Swallow, one species supplanting an- 

 other, i. 116 



Swaysland, Mr., on earth adhering to 

 the feet of migratory birds, ii. 156 



Swifts, nests of, i. 383 



Swimbladder, i. 256 



Switzerland, lake habitations of, i. 44 



System, natural, ii. 213 



Tail of giraffe, i. 271 



of aquatic animals, i. 272 



, prehensile, i. 321 



, rudimentary, ii. 270 



Tanais, dimorphic, i. 78 



Tarsi, deficient, i. 194 



Tausch, Dr., on umbelliferse, i. 297 



Teeth and hair correlated, i. 205 



, rudimentary, in embryonic calf, 



ii. 265, 302 

 Tegetmeier, Mr., on cells of bees, i. 



373, 379 

 Temminck, on distribution aiding 



classification, ii. 220 

 Tendrils, their development, i. 332 

 Thompson, Sir W. , on the age of the 



habitable world, ii. 89 

 , on the consolidation of the crust 



of the earth, ii. 284 

 Thouin, on grafts, ii. 25 

 Thrush, aquatic species of, i. 248 

 , mocking, of the Galapagos, ii. 



201-202 



, young of, spotted, ii. 251 



, nest of, i. 392 



