INDEX 



329 



Sensory organs, 107. 



Sex-limited inheritance, 233. 



Sexual differentiation, 147; re- 

 production, 141 ; in plants, 174. 



Sigma, in variation, 203. 



Skeletal structures, of animals, 

 110; in plants, 123. 



Skew curves, 204. 



"Sleep" in plants, 122. 



Soma-plasm, 150. 



Sparrow, variation, 211. 



Special creation, 299. 



Specialization, in conducting organs, 

 39 ; in digestion, 42 ; in loco- 

 motor organs, 32 ; and generali- 

 zation, 45. 



Species, Linnsean, 305 ; criteria of, 

 300 ff . ; elementary, 305 ; origin 

 of, 306, 313; meaning of term, 

 296. 



Specific energy, law of, 247. 



Spermatocyte, 154. 



Spiral valve, 106. 



Spirogyra, 146. 



Spore formation, 140. 



Sporophyte, 175. 



Starch, synthesis of, in the leaf, 53. 



Stature, variation in, 200. 



Stentor, regeneration in, 187. 



Stephanosphcera, 144. 



Stimulus, 243. 



Stomias boa, 264. 



Struggle for existence, 129. 



Stylonychia, 35. 



Substantive variation, 205. 



Suckers, 137. 



Sundew, 59. 



Surinam toad, 273. 



Survival of the fittest, 315. 



Suspended animation, 7. 



Syncytium, 91. 



Synthesis in the organism, 52. 



Synthetic products, artificial, 3. 



Syllis ramosa, 139. 



Tardigrades, 6. 

 Teleology, 195. 



Temperature, effect of, on response, 



244; on growth, 101. 

 Thyroiodin, 88. 

 Tiger butterfly, 302. 

 Tonus, 246. 

 Torpedo, 78. 

 Trichosphcerium, 151. 

 Trochosphcera, 261. 

 Tunicate, 40. 

 Typhlosole, 106. 



Unit characters, 223. ' 



Use and disuse in evolution, 317. 



Variation, 198; causes of, 212; 

 correlated, 209 ; discontinuous, 

 205 ff. ; effect of conditions upon, 

 211; Gallon's device, 201; in 

 human stature, 200; in beech 

 leaves, 202 ; types of curves, 

 202 ; substantive, 205. 



Vegetative reproduction, 133. 



Venus' flytrap, 59, 122. 



Vermiform appendix, 312. 



Vertebrate and invertebrate, 109. 



Vestigial structures, 312. 



Vitalism and mechanism, 194. 



Volvox globator, 149. 



Vorlicella, 37. 



Waller's criterion of life, 7. 

 Water, in protoplasm, 9. 

 Weismannism, 193. 

 Wheat, inheritance 'in, 235. 

 Wolff, K. F., 192. 

 Worms, parasitic, 288. 



Xerophytes, 276. 

 Xylolrupes, variation in, 205. 



Yeast, growth of, 131. 

 Yolk, 159. 



Zaitha, 272. 



Zoochlorella, 294. 



Zoospore, 174. 



Zygosis, 145 ; in animals, 155. 



Zymtgen, 85. 



Printed in the United States of America. 



