296 INDEX 
Yerkes, R. M., 190, 231, 258, Yoakum, C. 8., 259 
intelligence in Carcinus, Yung, E., 190 
184; in crayfish, 184; in 
frog, 228; in turtles, 230; Zell, T., 259 
variability of behavior in Zeigler, H. E., 114 
dancing mouse, 133, 134 Zurn, F. A., 259 
