404 



INDEX 



scales, 217 ; song of cicadas and birds, 

 221; superfluity of males, afs ; 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 CoccicUum pro- 

 prium, 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, period of, 25. 



Species, the, a complex of adaptations and 

 variations, ii. 307. 



Species-colonies, ii. 280. 



Species, extinction of, ii. 337 ; dying out 

 of the large animals of Central Europe, 

 ii. 361 ; extinction due to cultivation, ii. 

 360 ; to unlimited variation, ii. 357 ; 

 Machairodus, ii. 358 ; lower types more 

 capable of adaptation than higher, 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 Lepus variabilis, 

 ii. 344 ; Peridinese, 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. 



34°- 



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- ^99, 332-5- 



Spencer, Herbert, germinal substance com- 

 posed of homogeneous particles, 355 ; 

 on 'units,' the smallest vital particles, 

 369 ; protective adaptations in plants to 

 be referred to selection, ii. 77. 



Spermaries, 282. 



Spermatozoa, see Zoosperms. 



Sperm-cells, 272. 



Spermogenic determinants, 388. 



Sphingidse, caterpillars of the, biological 

 value of their markings, 73 ; ontogeny 

 and phylogeny of the markings, ii. 177. 



Sphinx convolvidi, double adaptation of the 

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

 Nicaia, purely local form of caterpillar, 

 362. 



Spontaneoiis generation, ii. 410 ; conditions 

 necessary, ii. 370 ; onlypcssibleasregards 

 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 {Ehijiina stetleri), 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 

 Amoebae, 170; green fresh- water polyp 

 {Hydra viridis), 168 ; Nostoc and AsoHa, 

 177; sea-anemones and yellow Algae, 

 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- 

 Thorn-bugs, 89. 



Transparent winged butterflies, 106. 

 Treviranus, as -founder of the evolution 



theory, 18 ; on generic differences, ii. 



306. 

 Trimen, observations on the immunity of 



the Acrfeidas, 100. 

 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. 



151; 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, Eudolf, on the inheritance of 



mutilations, ii. 65. 

 VOehting, influence of light on the pro- 



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