[Illustration:  FIG. 2.  Labyrinth as arranged for experiments. E, entrance; R, R, regions covered with red; W, W, regions covered with white.  The tracing represents the path taken by No. 2 on the sixth trial.  Dots mark jumps.]

TABLE II.

LABYRINTH HABIT.  FROG NO. 2.

Entrance.  Exit.  Remarks. 
Trials.  Right.  Wrong.  Right.  Wrong.
1- 10 1 9 4 6
One day rest.
11- 20 2 8 5 5
21- 30 4 6 7 3
31- 40 5 5 6 4
41- 50 5 5 6 2
(17) (33) (30) (20)
51- 60 9 1 8 2
61- 70 6 4 10 0
71- 80 7 3 9 1
81- 90 9 1 8 2
91-100 10(50) 0(10) 10(52) 0( 8)
—–­ —–­ —–­ —–­
67 43 82 28

Other animals which were used gave results so similar to those for frog No. 2 that I feel justified in presenting the latter as representative of the rapidity with which the green frog profits by experience.

TABLE III.

LABYRINTH HABIT.  FROG NO. 6a.

Entrance.  Exit.  Remarks. 
Trials Right.  Wrong.  Right.  Wrong.
1- 10 6 4 5 5
One day rest.
11- 20 7 3 4 6
21- 30 2 8 1 9
31- 40 6 4 1 9
41- 50 7 3 8 2
(28) (22) (19) (31)
51- 60 5 5 7 3
61- 70 6 4 4 6
71- 80 4 6 3 7
One day rest.
81- 90 5 5 7 3
91-100 10(30) 0(20) 8(29) 2(21)
——­ ——­ ——­ ——­
(58) (44) (48) (52)

Preliminary Trials.

Red on Left     Partition at Exit on Right
1- 5          5 times to Red       4 times to Partition.

Red on Right   Partition at Exit on Left
6-10          3 times to Red       5 times to Partition.

2. Rapidity of Habit Formation.—­As compared with other vertebrates whose rapidity of habit formation is known, the frog learns slowly.  Experimental studies on the dog, cat, mouse, chick and monkey furnish excellent evidence of the ability of these animals to profit quickly by experience through the adapting of their actions to new conditions.  They all show marked improvement after a few trials, and after from ten to thirty most of them have acquired perfect habits.  But the comparison of the frog with animals which are structurally more similar to it is of greater interest and value, and we have to inquire concerning the relation of habit formation in the frog to that of fishes and reptiles.  Few experimental studies with these animals have been made, and the material for comparison is therefore