560 'Journal of Comparative Neurology and Psychology. 



than those contributed by the distance receptors. These latter sense 

 organs frequently presented difficulties to the learning process rather 

 than actually assisting it. Such cannot be considered as rigidly 

 proved, but the general and specific behavior of the animals points 

 to such a conclusion. 



III. Tests on TempeexItuee Sense, 



The habit of the squirrels on cold days or whenever the tempera- 

 ture of the room became decidedly lower than usual, of burrowing 

 under shavings, sawdust or cotton, led to an attempt to devise means 

 of testing the temperature sense by the use of the discrimination 

 method. In this connection, the animal's method of covering itself 

 is interesting. The squirrel will draw the shavings, or cotton, up 

 in a pile in one corner of the cage, and will then burrow into it. 

 When finally hidden in the pile, all that is visible is a portion of 

 the tail; if this is drawn aside the tip of the nose and finally the 

 entire head become visible. The little animal thus lies curled up 

 in its nest with the tail as the final addition to its covering. 



The temperature test to be described was made in the first place 

 with a view to determining the general features of the temperature 

 sense; in the second place, for the purpose of testing the range and 

 fineness of this sense. The tests as originally planned are not com- 

 pleted. One of the animals was accidentally killed, and the work on 

 the other was stopped by reason of the experimenter's removal to 

 a distant locality. It is probably better to look upon these results 

 as being qualitative and preliminary rather than to consider them 

 as being standards quantitatively determined. 



The apparatus was constructed as follows: Two galvanized iron 

 boxes (A and B, Fig. 5) were made with outside dimensions of 

 9 X 9 X 24 inches. They were built like square-sided pipes, as 

 shown in the drawing, the inner opening being 5x5 inches and 

 running the entire length of the box. The space between the outer 

 and inner jackets was two inches deep and entirely enclosed the 

 central cavity with the exception of the ends. This enclosed space 

 was supplied with three vents, an inlet (I), an outlet (O) for the 

 water supply, and an air vent (V) to relieve the pressure when 



