24 



ROBERT M. YERKES AND JOHN B. WATSON 



addition to the above there are provided three forms which are- 

 inscribed in the aperture of the 6 cm. circle. They are (a) a 

 hexagon 3.000 cm. on the side; (b) a square 4.243 cm. on the 

 side; and (c) an equilateral triangle 5.196 cm. on the side. 



Figure 4 — Experiment box for brightness apparatus. Planned for kittens. A, 

 entrance chamber; B, discrimination chamber; C, partition; D, D, sliding 

 doors; E, E, electric passage-ways; P, partition; S, S, stimulus apertures; 

 F, F, doors for exits from E, E; I, I, pulleys for cords from I, I; G, G, alleys 

 to A; H, H, swinging doors. 



The experiment box differs from the light box and the stimulus 

 adapter in being a variable. The latter are permanent and may 

 be used for the study of any animal. The former, in every case, 

 must be adapted to the animal. The particular experiment box 



