34 IOWA STUDIES IN NATURAL HISTORY 
sand, was found with greater difficulty than the ones in the first 
and third partitions which were at the level of the sand, be- 
cause the animals habitually swam near the bottom. There is 
no evidence that these larvae recognized the apertures by the 
sense of sight until they were in close proximity to them. Di- 
rect observations indicate rather that the animals which did 
sometimes pass through the apertures without feeling their way 
1345678 12 415 19 20231 4 
Fig. 3. I, Il, and III, curves based on the first, second, and third 
trials, respectively, of all the animals in the second series. The or- 
dinates indicate the time in seconds; the abscissae, the days on which 
the trials were made. 
along the partitions retained an impression of the general lo- 
cation of the apertures which they had gained by previous ex- 
perience. The record also indicates that the second and third 
trials usually resulted in a successful passing through the maze 
in less time than the first. Curves I, II and III, fig. 3, are 
based on the average of the first, second and third trials respec- 
tively, of all the animals in the second series. While these 
curves show large variations from day to day, the general level 
of the second is materially lower than that of the first, and the 
