S Sable, 190 Saffron finch, 244 Sainfoin, 267 Salamander, 217, 219, 221 _Salix alba_, 118 _S. pentandra_, 118 Sandgrouse, 204, 351 Sandpipers, 185, 190 Sassaby, 363 _Satyridæ_, 205 Scatliff, H. P., 91-3 Scatliff strain, 91 Scaup, 290 Schmankewitsch, 156 “Science,” 166 _Sciuropterus volucella_, 243 _Scops giu_, 101 Scops owl, American, 44 ——, Indian, 101 Scoter, 249 Seal, 190, 191 Sea-urchin, 149 Seaweed, 263 Sebright, Sir John, 63 Secondary sexual characters, 298 Segregation, 369 —— of gametes, 143-5 Selous, Edmund, 308 —— F. C., 192, 195, 197, 203 Sematic colours, 173 _Sesia fuciformis_, 178 Sexual dimorphism, 51, 297-344 Sexual selection, theory of, 299-321 Shaheen, 251 Shamrock, 274 Sheathbill, 191 Sheep, 95, 266, 267, 283, 357, 372 Sheldrake, 109, 129 Shikra, 235, 236 Shoveler, 290 Shrew, 180, 216 Sidgwick, 28 Sidney, 5, 49 Sika deer, 120 Silver-washed fritillary butterfly, 103 Siskin, 127, 244 Skua, Arctic, 44, 362 Skua-gull, 191 Skunk, 186, 217, 221 Skylark, 315 Slug, 49, 185 Smith, Adam, 28 Snake, 185, 197, 198, 217, 220, 223-6, 247, 356 Snap-dragon, 268, 272 Snipe, 69, 327 Sodium sulphate, 151 Somatic variations, 106-10 “Some Indian Friends and Acquaintances,” 225, 358 Sorrel, 274 Sparrow, 213, 241, 341, 342 —— Java, 99, 100 Sparrow-hawk, 235, 243 _Spatula clypeata_, 290 Spavin, 332 “Species and Varieties,” 69, 77, 84, 87, 118 Species, definition of, 89 Species, elementary, 77, 78, 87-9 Spencer, 3, 15, 16, 28, 38, 151 Spider, 269, 272 _Sporæginthus amandava_, 311 Sports, 41, 43, 66, 75, 85, 135 Squirrel, 101, 186, 243 Stag, 325 —— Irish, 67 Standfuss, 155 Stanley crane, 248, 279 St Hilaire, T. G., 2, 356 Stick insect, 209 _Stictoptera annulosa_, 104 Stoat, 119, 190, 290 Stolzmann, 327-9, 342, 343 Stonechat, 353 Stork, 247, 282 “Strand Magazine,” 64 _Strix flammea_, 289 Struggle for existence, 31, 32, 48 —— for nourishment, 167 Suchetet, A., 126, 130 _Sula capensis_, 282 _S. serrator_, 282 Sunbird, 324 _Surniculus lugubris_, 235, 243 Survival of the fittest, 32 Survival value, 33, 34 Swallow, 250, 251, 279, 361 Swallow-shrike, 281 Swallow-tail butterfly, 179 Swan, 100 Swift, 243, 250 Swimming bladder of fishes, 36, 37 _Sycalis flaveola_, 244 _Syrphidæ_, 178