404 



INDEX 



scales, 217 ; song of cicadas and birds, 

 221; supertluity of males, 213 ; weapons 

 for the struggle for mates, 228 ; sum- 

 mary, 238. 



Selection value, ii. 132, 311. 



Self-fertilization in plants, ii. 252 ; con- 

 tinued influence of, ii. 257 : alternation 

 of self- with cross-fertilization, ii. 241. 



Self-preservation, instinct of, 144. 



Sex-cells, mutual attraction of, ii. 228. 



Sex, determination of, 377 ; ii. 44. 



Sexual characters, secondary, have their 

 roots in germinal selection, ii. 130, 143, 

 289-91, 378. 



Sexual selection, see Selection, sexual. 



Sexual selection through isolation, ii. 289. 



Short-sight, ii. 146. 



Siedlecky, copulation in Coccidium pro- 

 2)rium, ii. 218. 



Simroth, ii. 302. 



Slevogt, on birds as enemies of butterflies, 



97- 

 Sluiter, on symbiosis, 167. 



Smerinthus, markings of the caterpillars, 

 ii. 177, 184. 



Snail-strata of Steinheim, ii. 305. 



Sommer, on artificial epilepsy in guinea- 

 pigs, ii. 68. 



Special investigation, ])eriod of, 25. 



Species, the, a complex of adaptations and 

 variations, ii. 307. 



Species-colonies, ii. 280. 



Species, extinction of, ii. 357 ; dying out 

 of the large animals of Central Europe, 

 ii. 361 ; extinction due to cultivation, ii. 

 360 ; to vmlimited variation, ii. 357 ; 

 Machairodus, ii. 358 ; lower types more 

 capable of adaptation than liigher, ii. 

 359 ; extinction of flightless birds, ii. 

 360. 



Species-formation, ii. 299 ; favoured by 

 isolation, ii. 284 ; snails of Celebes, ii. 

 219 ; without amphigony in lichens, ii. 

 343 ; without isolation in Lejms variabilis, 

 ii. 344; Peridinete, ii. 325; protective 

 coloration in butterflies, ii. 310 ; the 

 Steinheim snail-strata, ii. 315; telescope 

 eyes in deep-sea animals, ii. 323 ; typical 

 species, ii. 304 ; variation in definite 

 directions, ii. 306 ; the bird as a complex 

 of adaptations, ii. 316 ; the whale as a 

 complex of adaptations, ii. 313 ; mutual 

 fertility between many plant-species, ii. 



340- 



Species, variable and constant, ii. 286. 



Specific type, its occurrence favoured by 

 germinal variation, ii. 333, 334 ; by 

 natural selection, ii. 334 ; origin of the, 



ii- 299. 332-5- 



Spencer, Herbert, germinal substance com- 

 posed of homogeneous particles, 355 ; 

 on 'units,' the smallest vital particles, 

 369 ; protective adaptations in ])lants to 

 be referred to selection, ii. 77. 



Spermaries, 282. 



Spermatozoa, see Zoosi)erms. 



Sperm-cells, 272. 



Spermogenic determinants, 388. 



Sphingi(ke, caterpillars of tlie, biological 

 value of their markings, 73 ; ontogeny 

 and i^hylogeny of the mai'kings, ii. 177. 



Si)hinx convolvuli, double adaptation of the 

 caterpillar, 71, 72 ; S. euphorhiit'. var. 

 yica-a, purely local form of caterpillar, 

 362. 



Spontaneous generation, ii. 410 ; conditions 

 necessary, ii. 370 ; only i^o-isibleasregards 

 invisible minute organisms, ii. 369 ; the 

 'where' of, ii. 371; impossibility of 

 proving or disproving it experimentally, 

 ii. 366. 



Sprengel, fertilization of flowers, 180. 



Standfuss, cold experiments with butterfly 

 pupse, ii. 275. 



Steinheim snail-strata, ii. 305. 



Steller's sea-cow (Rhijtina stelieri), ii. 74. 



Stick-insects, 88. 



Strasburger, fertilization of Phanerogams, 



314- 

 Stuhlmann, zoosperms in Ostracods, 276. 



Swammerdam, 14. 



Symbiosis, candelabra trees and ants, 171 ; 

 hermit-crabs and Hydroid polyps, 163 ; 

 hermit-crabs and sea-anemones, 162; 

 origin of symbiosis, 176; lichens, 173; 

 fishes and sea-anemones, 167 ; green 

 Amcebae, 170; green fresh- water polyji 

 {Hydra viridis), 168 ; Xostoc and Azolla, 

 177; sea-anemones and yellow Alga^, 

 171 ; root-fungi. 175. 



Talents, specific, of man referred to 

 germinal selection, ii. 149 ; depend on 

 a combination of mental gifts, ii. 150. 



Tichomiroff, artificial parthenogenesis, 307, 



333. 

 Tliorn-bugs, 89. 



Transparent winged butterflies, 106. 



Treviranus, as founder of the evolution 



theory, 18 ; on generic dift'erences, ii. 



306. 

 Trimen, observations on the immunity of 



the Acraeidie, too. 

 Tropism in plants, ii. 276. 

 Twins, identical, ii. 44. 



Vanessa, endemic species of, with protec- 

 tive colouring, 75. 

 Variability, fluctuating, ii. 327. 

 Variation, all ultimately quantitative, ii. 



J51 ; in a definite direction, ii. 118; 



double roots of, ii. 195 ; ascending, ii. 



122 ; sports or saltatory variations, ii. 



140 ; roots of hereditary, ii. 118. 

 Variation of individual characters, ii. 336 ; 



not always due to adaptation, ii. 197. 

 Variation, periods of, ii. 294. 

 Vital force, ii. 369, 

 Vitalism, ii. 369. 

 Virchow, Rudolf, on the inheritance of 



mutilations, ii. 65. 

 Vochting, influence of light on the pro- 



