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Figure 2. Ground plan of crow house, fly, and apparatus. Scale, T V- A, obser- 

 vation room; B, bird room; C, main portion of fly; D, passageway for experi- 

 menter; E, multiple choice box; F, entrance door between main fly, C, and 

 alley to reaction chamber, H; G, exit door between alley S and main fly; H, 

 reaction chamber, the floor boards of which are separated somewhat; I, L, 

 approaches to the doors F and G; J, observer's table and key-board; K, observ- 

 er's stool; N, doors for experimenter's use; P, perches; R, alley leading to 

 middle of reaction chamber H; S, alley leading from exits to main fly; W, 

 water tub for crows. 



Numerals 1 to 9, compartments of multiple choice box; a, attachment of 

 cord to entrance door, t, of compartment 9; b, screw eye for cord; c, screw eye 

 at entrance to observer's room; d, wooden button on cord; under d is a small 

 brass pulley for cord; h, i, j, k, indicate course of cord from exit door of com- 

 partment 9 to key-board; x, metal cover for food receptacle of compartment 

 9; z, food receptacle of compartment 4. 



