On the basis of two tests per day, two common mice, a white one and a gray one, quickly learned to escape from labyrinth _A_ by the shortest path. The time of escape for the gray individual (Table 37) decreased from 180" in the first test to 21" in the tenth, and the number of errors from 6 to 1. Similarly in the case of the white individual, the time decreased from 122" to 8", and the errors from 5 to 1. A fraction of the number of tests to which the dancer had been subjected sufficed to establish a habit of escape in the common mouse. It is evident, therefore, that the dancer differs radically from the common mouse in its behavior in a maze, and it is also clear that the labyrinth method, if it is to be used to advantage, must be adapted to the motor tendencies of the animal which is to be tested. TABLE 37 RESULTS OF LABYRINTH A TESTS WITH COMMON MICE GREY MOUSE WHITE MOUSE TEST T E T E 1 180" 6 122" 5 2 26 2 80 6 3 37 1 56 4 4 18 0 27 1 5 68 2 33 2 6 10 1 19 1 7 11 1 17 1 8 13 1 17 1 9 10 0 8 1 10 21 1 8 1 The behavior of the dancer made obvious two defects in labyrinth A. Its passages are so large that the mouse is constantly tempted to dance, and it lacks the basis for a strong and constant motive of escape by the direct path. To obviate these shortcomings labyrinth B was constructed, as is shown in Figures 23 and 24, with very narrow passages, and a floor which was covered with the wires of an interrupted electric circuit so that errors might be punished. The length of this labyrinth was 52 cm. and the passages were 2.5 cm. wide and 10 cm. deep. Dancing in these narrow alleys was practically impossible, for the mice could barely turn around in them. In the case of all except the common mice and two dancers, a depth of 10 cm. was sufficient to keep the animals in the maze without the use of a cover. As an account of the behavior of the dancer in labyrinth B has already been given in Chapter XI, I may now state the general results of the experiments. In all, thirty individuals were trained in this labyrinth. Each individual was given tests at the rate of one per minute until it had succeeded in following the correct path five times in succession. The weak electric shock, which was given as a punishment for mistakes, provided an activity-impelling motive for escape to the nest-box.