422 



INDEX 



von Schweppenburg, origin of sub- 

 species, 140 



Sciurus, races of, 114, 116 



— , specific intergradation, 89 



Sciurus carolinensis , change of habits, 55 



, spread, 322 



Scorpions, adaptive differences, 283 



— , trends in, 78 



Scott, uniformity of species of marine 

 Crustacea, no 



Scudder, change in population of 

 Pieris, 213 



Seasonal occurrence, in relation to 

 isolation, 142 



— variation in Cladocera, 1 2 

 Segregation ' en bloc,' 1 70 



— of specific characters, 172 

 Seitz, species-recognition, 148 

 Selachians, copulatory fins, 297 

 Selection, artificial, 188-92 



— , experiments on Drosophila, 204-5 

 — , role in origin of domesticated races, 



190 

 — , also see Natural Selection 

 Selective mating, 99, 143 

 Semenov-Tian-Shansky, use of term 



' natio,' 70 

 Senescence, 329-30 

 Sepia, breeding seasons of races, 1 45 

 Sex-ratio, local variation in Hypolimnas, 



124 

 Sexton and others, viability of Gam- 



marus-mutants, 222 

 Sexual selection, 272, 291-300 

 Sheldon, polymorphism in Acalla, 102 

 Shelford, distribution of Tiger Beetles, 



Shipworm, Giant, size, 333 

 Sikora, races of lice, 75 

 Silfrast, experiments on Cavia, 36 

 Silkworm, inheritance in, 53 

 Simocephalus, experiments on, 39 

 Sitona, variation in wing-length, 197 

 Size, exaggerated, general, 333 

 — , exaggerated, of parts, 331 

 — , influence on dispersal, 1 10 

 — , relation to isolation, 105, 141 

 — , variation in, determined by food- 

 supply, 79 

 Skeleton, external, as controller of en- 

 vironment, 360 

 Skomer Vole, smallness of area occu- 

 pied, 1 1 7 

 Slipper Limpet, spread of, 322 

 Slugs, polymorphism, 101 

 Smilodon, excessive growth of teeth, 



335 

 Smuts, on Holism, 344 

 Smynthurus, fluctuations in population, 



359 

 — , optimum conditions, 358 



Snakes, blind, adaptive differences, 286 

 — , Garter, determinate evolution, 325 

 — , mimicry, 243 

 Snodgrass, non-environmental trend 



in Geospizo, 78 

 Song, differences in, 120-21 

 Sonneborn, criticism of Macdougall's 



experiments on rats, 28, 40 

 Sparrow, see Passer 

 Specialisation, 349 

 — , in relation to adaptation, 364-66, 



.370 

 Species, 61 

 — , ' adaptable,' 350 

 — , age of, 171 

 — , effect of abundance on variation, 



134 

 — , hereditary stability of, 63 



— , intergradation of, 89, 103 

 — , introduced, 306 

 — , Lotsy's views, 73 

 — , method of fission, 298, 302 

 — , in palaeontology, 65 

 — , parent and variety living together, 

 Bronn's and Darwin's views, 183 

 — , range including varied types of 



country, 356-57 

 — , simple and compound, 73 

 ■ — , stability of, 137 

 — , also see Groups 



Specific characters, adaptive value 

 examined in special cases, 

 274-306 



, correlation of, 1 62 and foil. 



, evolution of, 366 



, in models and mimics, 261-62 



, secondary sexual, types of, 292 



Sphaerium, correlation in, 164 

 Sphaeroceridae, seasonal occurrence, 



144 

 Spiders, courtship, 150 

 — , grasping organs, 294 

 — , insular forms, 135 

 — , scent-production, 293 

 Spilosoma, viability of melanics, 214 

 Spirifer, senescence, 330 

 Sponges, modifications of, 81 

 Spontaneous mutation, 29 

 Spread, of introduced species, 322 

 ■ — , of variants, 306 

 Squirrels, see Sciurus 

 Standfuss, experiments on Vanessa, 36 

 — , mating between races of moths, 150 

 Statistical methods, limitations of, 9-10 

 Stegosauria, exaggerated size of plates, 



33 l 

 Stephenson, J., variation in Oligo- 



chaetes, 1 10 



Stephenson, T. A., methods of re- 

 production as specific characters, 123 



Sterility, 74, 156 and foil. 



