232 



The Mechanistic Conception of Life 



Selection, ol intensity of liglit by ani- 

 mals, 52 ff. ; natural, 50 fl. 



Sex determination, 16. 



Shearer, 11. 



Sipunculides, 141. 



Snyder, C. D., 39, 208. 



Solution, protective, 172. 



SpaUanzani, 113. 



Spermatozoa, 113 fl. 



Spermatozoon, twofold action of, in 

 fertilization, 12 fl., 132 fl., 161 fl. 



"Speziflsche Bildungsstofle," 104. 



Spirogyra. 177 fl., 188. 



Spontaneous movements, 71. 



Standtuss, 211. 



Stereotropism, 91 fl., 223. 



Stevens, 17. 



Stieglitz, 43. 



Stockard, 206, 207. 



Strongylocentrotus franciscanua, 140, 

 198. 



Strongylocentrotus purpuratus, 8, 139 fl., 

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



Sumner, 80. 



Symmetry, chemical, 38, 39. 



Temperature as a cytolytic agent, 



135 fl., 138 fl. 

 Tower, 90, 227. 

 Traube, 96. 

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



69, 70, 72. 

 Tubularia mesembryanthemum, 95, 97. 

 Tunicates, 92. 

 Twin formation, 19, 205. 

 Twins, production of, from egg. 204 fl. 

 Twofold action of spermatozoon in 



fertiUzation, 12 fl., 132 fl., 161 H. 



Tyrosin, 23. 



TTexkuell, 70. 

 "Unterschiedsempflndlichkeit," 54. 



Van Duyne, 92. 



van't Hofl, 208. 



Vanessa antiope, 220. 



Vanessa levana, 211. 



Vanessa prorsa, 211. 



Varying photosensitiveness in animals, 



45. 

 Varying susceptibility of eggs of 



diflerent species to parthenogenetic 



development, 144. 

 V aucheria, 188. 

 Virchow, 127, 128. 

 Vision, 79 fl. 

 Volt, 4. 

 Volmx, 51, 223. 



WaUer, A. D., 222. 



Warburg, 13, 157, 160. 189, 190. 



Wasteneys, 13, 157, 181, 182. 



Water, distilled, poisonous action of 



distilled water on. 170 fl.; rOle of, 



in segmentation, 99. 

 Weismann, 91, 210, 211. 

 Wiener, 215. 

 "Will," 35 fl., 40. 

 WUson, 17, 18, 19. 



X-chromosomes, 18 fl. 



"Zielstrebigkeit," 24. 

 Zimtz, 4. 



