14 



obtained aocurately by means of the camera lucida attachment de- 

 signed by rrof. 'w'atson (see plate I) for use with hia circular 

 mas^e. This maze has a wooden base 150 om. in diameter and six 

 aluminum runways 15.5 cm. high and 10 cm. v.ide. The entrances 

 to the alleys are 10 cm. wide, and are at alternate ends of a 

 quadrant arc. The radial stops in alleys 1 to £ are also i^lac- 

 ed at alternate ends of a quadrant arc, the stoi. in each alley 

 being directly opposite its entrance. Thus it is possible for 

 a rat to run only l/S the circumference of a runway in either 

 direction before being forced to turn. This is not true of 

 ailey 6, where no stop is employed. The central circle, or 

 food compartment is 20 cm. in diameter. A 3/4 inch mesh, wire 

 top prevents the animals from escaping v.ithout interfering with 

 observations of their movements. The camera lucida attachment 

 consists primarily of tvvo mirrors and an achromatic lens. The 

 arrangement is as follows: A large plate glass mirror is fas- 

 tened by sui porting framework at an angle of. 45° v\ith its cen- 

 ter directly above and 1.8 meters from the center of the maze. 

 A somewhat smaller mirror is placed facing the first and making 

 an angle of 90° with it at such a distance away that t.:e light 

 reflected downward fal"'s outside the maze area. In the path 

 of this reflected light is placed a single achromat, 6 om. in 

 diameter and of 50 cm. focus^ in a mounting provided with rack 

 and pinion adjustment which is fitted into the ceiiter of a 

 wooden disc 30 cm. in diameter. Below this at the focus of 

 the lens is jlaced a second wooden disc of the same diameter as 

 the first, which serves as a holder for the paper Ui.on which 



