4o8 



INDEX 



Sylvius, founder of iatrochemical 



school, 6. 

 System, harmonious equipotential, 



375- 



Talorchestia, 271. 



Temora longicornis, 284; 300. 



Temperature, effect of, on reversal 

 in reactions, 272-279, 300; effect 

 of, compared with that of light, 

 276, 367; extent of effect of, on 

 reversal in reactions, 277. 



Tenebrio, 346. 



Theory, of orientation in plants: 

 De Candolle, 12, Sachs, 13-16, 

 Darwin, 18-21; Loeb: first theory 

 of orientation (ray direction), 24, 

 25, 34, second theory (angle of 

 rays), 28, 29, 35, third theory 

 (intensity difference), 29-31, 35; 

 of orientation in animals (Daven- 

 port), 40-42; Radl's, 42, 43; Jen- 

 nings' (trial and error), 46-49; 

 Torrey's, 84, 85; Holmes', 218; 

 Graber's, 218; of local response 

 to local stimulation, 86. See 

 Criticism. 



Threshold, in Euglena, 104-106; in 

 Stentor, 114, 115, 119; in plants, 

 288; in Volvox, 289-291. 



Thyone briareus, 212; reactions to 

 shadows, 247. 



Tissue, sensitive, distribution of: as 

 a factor in orientation, 3, in 

 plants, 21, 59, 71, in Hydra, 156, 

 157, in Arenicola larvae, 172, in 

 ]\Iusca larvae, 183, 184, 188, 197, 

 in earthworm, 201, 205; effect of, 

 in reactions, 261, 262. 



Toads. See Bufo and Frogs. 



Torelle, 214; reactions of frogs to 

 light and shadow, 218, 219; 222; 

 223; 244; reversal in reactions 

 (frog), 273. 



Torrey, definition of tropism, 56; 57; 

 criticism of Jennings on Euglena, 

 84, 85; 89; 100; loi; 104; 112; 205. 



Towle, effect of mechanical stimu- 

 lation on reaction, 284. 



Trachelomonas, orientation in light 

 from two sources, 87; function of 

 eye-spot, 109, 130; description of, 

 128; structure of eye-spot, 128, 

 129; accuracy of orientation, 129; 

 mechanics of orientation, 129, 130; 

 146; 229; 230; aggregation of, 241; 



257; 259- 

 Trembley, 33, 34; observations on 



movements of Hydra, 148, 149. 



Trial and error, orientation by, 46; 

 in Euglena, 99; in Stentor, 123; 

 in Volvox, 142, 145; in Euden- 

 drium, 162; in JMusca larvae, 196; 

 in earthworms, 198, 199, 203, 206; 

 214; defined by Jennings, 215; 

 Engelmann on, 240. 



Titicum vulgare, 66. 



Trochophores, Hydroides, 87. 



Tropaeolum, 59; 68; 72. 



Tropism, introduction of term and 

 original meaning, 11, 23, 52; de- 

 fined, 53-57; 83. 



Uca pugnax. See Fiddler Crab. 



Uexkiill, von, 212; 247; 248. 



Ulothrix, 274. 



Ultra-violet, effect of, on: Paramecia, 

 134, 135, Daphnia, 339, 343, chemi- 

 cal reactions, 310, 311, 360, ants, 

 349, seedlings, 314, 315, 319, 

 Lumbricus, 345; cause of invisi- 

 bility of, 362; 368. 



Ulva lactua, 274. 



Unterschiedsempfindlichkeit, com- 

 pared with motor reflex, 17; 27; 



2>y, 85; 94; 114; lis; 241; 243; 

 compared with heliotropism, 254- 

 256; 258. 



