56 IOWA STUDIES IN NATURAL HISTORY 
resulted in an average interval of 6 minutes and 31 seconds 
during which the meat lay on the bottom of the aquarium before 
it was seized and eaten. 
On the following day the five blinded animals were again 
placed in the circular aquarium in water 3 inches in depth. 
Crayfish’s meat was held by means of a pair of forceps just 
beneath the surface of the water near the center of the aquar- 
ium. The animals showed by their general behavior that they 
recognized the presence of food and apparently searched for 
it. However, none of them succeeded in finding it during an 
interval of ten minutes. At the close of this interval a bit of 
crayfish’s meat dropped on the bottom at the center of the 
aquarium was seized in 25 seconds. 
The results of the above experiment show clearly that while 
the normal animals discover food suspended in the water more 
readily than food lying on the bottom, the blinded animals dis- 
cover food lying on the bottom more readily than food sus- 
pended in the water. As pointed out above, the normal ani- 
mals detect food suspended or moving in the water largely by 
the sense of sight. The blinded animals rarely moved away 
from the walls or floor of the aquarium while searching for 
food. They apparently depended on contact for guidance in 
their movements. They could readily find food on the floor 
of the aquarium, being attracted by its odor; however, they 
could not find food suspended in the water because they groped 
along the walls of the aquarium. The more strongly they were 
stimulated by the odor of the food the more vigorous became 
their movements; consequently, the more closely they clung 
to the walls of the aquarium. 
In order to test the olfactory sense still further these blind- 
ed animals were offered pledgets of cotton some of which were 
soaked in water, others in a watery extract of crayfish’s meat. 
They manifested no interest in the pledgets of cotton soaked 
in water; however, when the pledgets of cotton soaked in the 
extract of crayfish’s meat were presented they were promptly 
seized and in some instances swallowed. In some instances an 
attempt to swallow the cotton failed, and it was rejected after 
several movements of the jaws. After having seized several 
bits of cotton soaked in the extract of crayfish’s meat two of 
