558 



KARL T. W.U'(JH 



Fig. 3 Visual discrimination apparatus. A, nest box; B, entrance chamber; 

 ft, ft, red ray-filter; G, green ray-filter; L, L, incandescent lamps in light box; 

 S, millimeter scale on light box; /, door between A and B; O, 0, doors between 

 alleys and A. (Verkes. The Dancing Mouse, p. 153. 1907. The Macmillan Co.. 



N. Y.) 



