350 C. II. TURXKR. 



climb up lo the top of it, meander around and then descend and 

 go to some other part of the maze. Hence a cardboard incline, 

 r\ tending from some definite part of the maze to the jelly glass 

 that had served as a cage for the roach, was substituted for the 

 dark box. 



This same series of experiments taught me that the best place 

 for the incline to leave the maze was the point labeled "C." 

 To be of value the incline should be located where the roach, in 

 roaming about the maze, is sure to accidentally discover it. It 

 was found that, in almost all cases, a roach, on reaching the junc- 

 tion of 7, C and 8, turned into 8 and, after passing into D and 

 often into E, retraced its steps and entered C; hence an incline 

 placed at E would have been too easy a problem. It was noticed 

 that roaches seldom entered 9; hence to place the incline at the 

 extremity of either 1 1 or G would be making the task too difficult. 

 C seemed the golden mean. 



The roaches used as the subjects of these experiments were 

 isolated in jelly glasses and given an abundance of food. No 

 roach was used in an experiment until it had been in its jelly- 

 glass cage for several days. This was done to get the roach 

 accustomed to confinement and to my presence. The roaches 

 used were females varying in size from young ones ten milli- 

 meters in length to full-grown individuals. 



The roach to be tested was always placed on 1. This was 

 done in two different ways. Sometimes the hind leg of a roach 

 was grasped in a pair of forceps and the roach placed on /; at 

 others, by means of forceps, the roach was transferred from its 

 glass cage to a narrow cylindrical beaker. This glass was then 

 covered with a small piece of paper and the whole inverted on 

 the maze at I. The paper was then removed, and, as soon as 

 the roach quieted down, the cylindrical glass was removed. If a 

 roach ran the maze three times in succession without making an 

 error, it was considered to have solved it. After each trial, the 

 surface and the edges of the maze were painted with alcohol to 

 remove any odor that might have been deposited by the roach. 



For convenience, the errors made were grouped under two 

 heads: those which resulted in the roach falling into the water 

 and those made by the roach while remaining on the maze. 



