there is seldom any hesitation at the turning points. The irregular labyrinth is followed carefully, as by choice of the path from point to point; the regular labyrinth is followed in machine fashion,--once started, the animal dashes through it. TABLE 40 RESULTS OF LABYRINTH-D EXPERIMENTS, WITH TWENTY DANCERS MALES FEMALES NO. OF NO. OF FIRST NO. OF LAST OF NO. OF NO. OF FIRST NO. OF LAST OF MOUSE CORRECT TWO CORRECT MOUSE CORRECT TWO CORRECT TEST TESTS TEST TESTS 2 3 7 29 10 11 58 7 10 49 7 8 30 9 10 57 3 6 60 10 14 215 6 10 402 10 11 415 7 8 76 4 7 75 4 13 78 4 5 77 11 12 86 3 9 87 4 9 88 4 8 85 3 4 90 7 8 83 4 7 Av. 6.1 8.9 Av. 5.9 8.8 From the results of these labyrinth experiments with dancers I am led to conclude that a standard maze for testing the modifiability of behavior of different kinds of animals should be constructed in conformity with the following suggestions. Errors by turning to the right, to the left, and by moving forward should occur with equal frequency, and in such order that no particular kind of error occurs repeatedly in succession. If we should designate these three types of mistake by the letters _r, l_, and _s_ respectively, the error series of labyrinth C would read _l-l-r-s-l_. It therefore violates the rule of construction which I have just formulated. In the case of labyrinth D the series would read _l-s-r-s-l-s-r-s-l-s-r-s- l_. This also fails to conform with the requirement, for there are three errors of the first type, four of the second, and six of the third. Again, in a standard maze, the blind alleys should all be of the same length, and care should be taken to provide a sufficiently strong and uniform motive for escape. In the case of one animal the desire to escape from confinement may prove a satisfactory motive; in the case of another, the desire for food may conveniently supplement the dislike of confinement; and in still other cases it may appear that some form of punishment for errors is the only satisfactory basis of a motive for escape. Readers of this account of the behavior of the dancing mouse must not infer from my experimental results that the electric shock as a means of forcing discrimination will prove satisfactory in work with other animals or even with all other mammals. As a matter of fact it has already been proved by Doctor G.