animal in its course until other sensory data determined the next move.  When the wrong passage had been chosen the visual data gotten from the appearance of the partition which blocked the path and other characteristics of this side of the labyrinth determined that the organism should respond by turning back.  When, on the other hand, the open passage had been selected, a moment’s halt sufficed to give sensory data which determined the continuation of the forward movement.  Although this reaction did not occur in more than one tenth of the trials, it was so definite in its phases as to warrant the statements here made.  Fig. 4 gives the path taken by No. 2 in its 123d trial.  In this experiment both choices were correctly made, but when the frog touched the wires on the open side it stopped short and wheeled around; after a moment it turned toward the exit again, but only to reverse its position a second time.  Soon it turned to the exit again, and this time started forward, taking a direct course to the tank.  The usual course for animals which had thoroughly learned the way to the tank is that chosen in Fig. 5.

[Illustration:  FIG. 4.  Path of No. 2 for 123d Trial.  Showing the response to the tactual stimulus from wires.]

An interesting instance of the repetition of a reaction occurred in these experiments.  A frog would sometimes, when it was first placed in the box, by a strong jump get up to the edge; it seldom jumped over, but instead caught hold of the edge and balanced itself there until exhaustion caused it to fall or until it was taken away.  Why an animal should repeat an action of the nature of this is not clear, but almost invariably the second trial resulted in the same kind of reaction.  The animal would stop at the same point in the box at which it had previously jumped, and if it did not jump, it would look up as if preparing to do so.  Even after a frog had learned the way to the tank such an action as this would now and then occur, and almost always there would follow repetition in the manner described.

[Illustration:  FIG. 5.  Path Usually Taken by Animal Having Perfectly-formed Habit.]

4. The Effect of Fear upon Habit Formation.—­A certain amount of excitement undoubtedly promotes the formation of associations, but when the animal is frightened the opposite is true.  I have no hesitation in stating that, in case of the green frog, any strong disturbing stimulus retards the formation of associations.  Although the frogs gave little evidence of fear by movements after being kept in the laboratory for a few weeks, they were really very timid, and the presence of any strange object influenced all their reactions.  Quiescence, it is to be remembered, is as frequently a sign of fear as is movement, and one is never safe in saying that the frog is not disturbed just because it does not jump.  The influence of the experimenter’s presence in the room with the frogs which were being tried