4IO 



INDEX 



Yerkes, Ada W., reactions of Hy- 

 droides and modification in, 249, 

 292, 293. 



Yerkes, R. M., definition of tropism 

 (phototaxis, photopathy), 55; 63; 

 reactions of Gonionemus, 164; 214; 

 251; classification of reactions to 

 light, 255, 256; 266; 274; reactions 



of Simocephalus in spectrum, 341- 

 343; 360. 



Zea mays, orientation of plumules, 



59-73, 229. 

 Zoeae, orientation in light from 



two sources, 87; 226; 243; 277; 



280. 



