LEARNING OF MAZE BY AMBYSTOMA 33 
Curve AD, fig. 2, illustrates the record made by a single in- 
dividual (No. 2 in the second series). From the average ini- 
tial interval of 105.7 see. the curve rises to 146 for the second 
series of trials, but then drops rapidly to 29.3. for the fourth 
series, and does not again rise above 54 during the successive 
series of trials and terminates at 30 for the 13th series of trials 
on the 21st day following the initial series. 
These several curves indicate that the late larvae of Amby- 
stoma tigrinum are able, by repetition, to form simple habits. 
The most rapid progress is indicated early in the experiment. 
The curves drop rapidly until a more or less constant level is 
reached. Curve AC indicates a second drop following the 15th 
day; however, the experiment was not continued long enough to 
determine whether or not a new low level would have been es- 
tablished. 
After the 8th day the animals were not again subjected to 
experiment until the 12th day. The average interval required 
to pass through the maze on the 12th day was 28.6 seconds 
longer than the average for the four days preceding the 8th 
day. Again the experiment was interrupted from the 15th to 
the 19th day. The average interval on the 19th day was 33.1 
seconds shorter than the average interval on the 15th day, and 
22.8 seconds shorter than the average for the 14th and 15th 
days. Therefore, the record affords no evidence that after the 
first low level was established the animals were less able to ac- 
complish the task set before them after a period of rest of four 
days than they were at the beginning of that period. Obviously 
the simple habits formed were retained during this short inter- 
val. 
Direct observations indicate that the animals gradually be- 
came more and more familiar with the maze during the pro- 
gress of the experiment, and were able to pass through it with 
appreciably less effort than in the initial trials. Whereas early 
in the experiment they usually felt their way along the walls 
of the aquarium and the partitions and passed through the 
apertures only when they were found in this manner, later some 
of the animals not infrequently passed through the apertures 
without feeling their way along the partitions. The aperture 
in the middle partition, which was 4 em. above the level of the 
