DISCRIMINATIVE ABILITY OF THE TURTLE 3 



ability in this respect is evident, it may be concluded that such 

 visual powers have played some part at least in bringing to the 

 mind of the adult animal a realization of the nature of its more 

 intimate surroundings. With the results of such an investi- 

 gation this paper is chiefly concerned. 



DESCRIPTION OF APPARATUS 



The apparatus used in all tests is similar in nature to the 

 electric-box apparatus of Yerkes' though somewhat modified 

 to make it more adaptable to the habits of turtles. It is shown 

 in relief in Fig. I and in ground plan with boxes removed in 

 Fig. II. The large oblong box in which all of the other appa- 

 ratus is placed (except some of the electrical connections) is 

 of heavy galvanized sheet-iron, 78 cm. long, 38 cm. wide and 

 with sides 16 cm. high. It is divided into three regions: an 

 entrance room at one end, an insulated area at the other, on 

 which the boxes stand, and a runway between. The entrance 

 room can be shut off from the runway by dropping the slide 

 operated by a string which runs behind the screen. The insula- 

 tion plate upon which the electric and food boxes stand is of 

 beeswax. It stands 4^ cm. above the floor of the large galvan- 

 ized box. The floor of the runway and entrance room is covered 

 with clean, washed sand, which in the runway is banked up to 

 form a gentle slope leading from the sand covered bottom to 

 the level of the insulation. Water to a depth of 3 cm. covers 

 the bottom of the entrance room and part of the runway. The 

 shallow water and the sandy approach to the boxes are, of 

 course, simply artificial environmental conditions used in an 

 endeavor to simulate natural conditions. 



The long metal electrode extending in front of the boxes is 

 kept in electrical connection with the water by means of the 

 wet sand which surrounds it. The two metal plates embedded 

 in the insulation are connected with the switch which is in 

 turn connected with the rheostat. The other pole of the rheo- 

 stat is connected with the water. By means of the switch the 

 current may be directed to either one of the insulated elec- 

 trodes. This switch is located behind the screen which conceals 

 the operator from observation. A small peep-hole through the 



' Yerkes, R. M., The Dancing Mouse. New York: The Macmillan Company. 1907, 



