232 



The Mechanistic Conception of Life 



Selection, of intensity of light by ani- 

 mals, 52flf.; natural, 50 flf. 



Sex determination, 16. 



Shearer, 11. 



Sipunculides, 141. 



Snyder, C. D., 39, 208. 



Solution, protective, 172. 



Spallanzani, 113. 



Spermatozoa, 113 fl. 



Spermatozoon, twofold action of, in 

 fertilization, 12 ff., 132 flf., 161 flf. 



"Speziflsche Bildungsstoflfe," 104. 



Spontaneous movements, 71. 



Spyrogyra, 177 flf., 188. 



Standfuss, 211. 



Stereotropism, 91 flf., 223. 



Stevens, 17. 



Stieglitz, 43. 



Stockard, 206, 207. 



Strongylocentrotus franciscanus, 140, 

 198. 



Strongylocentrotus purpuratus, 8, 139 flf., 

 144, 162, 189, 197, 201, 205. 



Sumner, 80. 



Symmetry, chemical, 38, 39. 



Temperature as a cytolytic agent, 



135 flf., 138 flf. 

 Tower. 90, 227. 

 Traube, 96. 

 Tropisms, 26, 36 flf., 54, 55, 60, 62, 



69, 70, 72. 

 Tubularia mesembryanthemum, 95, 97. 

 Tunicates, 92. 

 Twin formation, 19, 205. 

 Twins, production of, from egg, 204 flf. 

 Twofold action of spermatozoon in 



fertilization, 12 flf., 132 flf., 161 flf. 



TjTosin, 23. 



Uexkuell. 70. 



" Unterschiedsempfindlichkeit," 54. 



Van Duyne, 92. 



van't Hoflf, 208. 



Vanessa antiope, 220. 



Vanessa levana, 211. 



Vanessa prorsa, 211. 



Varying photosensitiveness in animals, 



45. 

 Varying susceptibility of eggs of 



dififerent species to parthenogenetic 



development, 144. 

 Vaucheria, 188. 

 Virchow, 127, 128, 

 Vision, 79 flf. 

 Voit, 4. 

 Volvox, 51, 223. 



Waller, A. D., 222. 



Warbiu-g, 13, 157, 160, 189. 190. 



Wasteneys, 13, 157, 181, 182. 



Water, distilled, poisonous action of 



distilled water on, 170 flf. ; role of, 



in segmentation, 99. 

 Weismann, 91, 210, 211. 

 Wiener, 215. 

 "Will," 35 flf., 40. 

 Wilson, 17, 18, 19. 



X-chromosomes, 18 flf. 



"Zielstrebigkeit," 24. 

 Zuntz, 4. 



