30 IOWA STUDIES IN NATURAL HISTORY 
der to approach the shaded area, to turn to the left, it was now 
necessary to turn to the right. Nevertheless, the animal turned 
toward the shaded area without exception in ten successive 
trials. 
The above experiment indicates clearly that the larvae of Am- 
bystoma are capable of finding a shaded area at the end of the 
aquarium toward the sun quite as readily as at the opposite 
end; consequently, the maze was arranged in this manner. For 
the first series of four larvae two partitions of ordinary painted 
window screen were placed transversely in the aquarium, ap- 
proximately 20 and 40 em., respectively, from the unshaded 
end. The first partition contained a rectangular aperture 2.5 em. 
in width, the lower border of which stood approximately 4 em. 
above the sand and 2 em. below the surface of the water. The 
second partition contained an aperture of 2.5 em. square, the 
lower border of which was at the level of the sand. The larvae 
were placed in the aquarium without the partitions in place un- 
til they became accustomed to seeking the shaded area. The 
partitions were then put in place. Each of the animals in turn 
was placed in the compartment at the unshaded end of the 
aquarium and the time noted until it had passed through the 
apertures in the partitions and reached the shaded area. Each 
animal was given three successive trials. These larvae were 
not again placed in the maze until two days later.. Each ani- 
mal was again placed in the aquarium without the partitions in 
place and permitted to seek the shaded area three times. The 
partitions were then replaced and each animal was given three 
trials to reach the shaded area by passing through the apertures. 
These exepriments were repeated on five successive days. On 
the third day one of the larvae had become sluggish by reason of 
its approaching metamorphosis and was discarded. After this 
the series included only three animals. Curve AB, fig. 2, is 
based on the averages of all the trials of all the animals in the 
series. The ordinates indicate the time in seconds required for 
the animal to pass from the compartment at the unshaded end 
of the aquarium through the apertures in the partitions to the 
shaded area at the opposite end. The abscissae indicate the 
days on which the trials were made. This curve drops rapidly 
' from 206.5, which is the average of the first series of trials, to 
