INSTINCTS AND HABITS IN CHICKS 



43 



dimensions and details may be clearly supplied. From the 

 entrance box A, i6 by 20 cm., the chick was released by a wire 

 screen door of .86 cm. mesh that was raised and lowered in its 

 grooves at B by the experimenter. This retaining screen was 

 shaped so that its lower edge coincided with an arc of a circle 

 constructed from the center above referred to. The width of 

 the opening at B was 10 cm. The first cardholders were at 

 D, the passage ways through which were 9.33 cm. wide. Through 



Figure 8 — Ground plan of apparatus for testing habit-formation. A, entrance 

 box- B wire-screen door; D and F, location of card-holders; E,E, electric 

 chambers; G, H, I, way out of box; K, electric key; L, electric battery; M, 

 inductorium. 



D the chick passed into the electric chamber E, the floor of 

 which was crossed with copper wires i cm. apart, so arranged 

 that they formed an interrupted circuit which could be closed 

 by the chick when the current was on by its stepping simul- 

 taneously on two adjoining wires. Out of E the chick passed 

 through the opening F, 8.5 cm. wide, the position of the second 

 card. From G there was an. outlook through the wire netting 



