54 IOWA STUDIES IN NATURAL HISTORY 
the water. Twenty-five trials resulted in an average interval 
of 15.2 seconds from the time the meat was lowered into the 
water until it was seized. 
Obviously, in the above experiments the food was detected 
by the sense of sight. Doubtless the detection of food in the 
water by the olfactory sense would require longer time inter- 
vals. The results indicate that the animals respond more’ 
promptly after savory food has been tasted than in the initial 
trials. They also indicate that these animals become interested 
in and approach moving objects much more promptly than ob- 
jects which are not in motion. 
In another experiment with the same animals in the aqua- 
rium, a bit of meat was dropped on the sand at the bottom. Fif- 
teen trials resulted in an average interval of 3 minutes and 18 
seconds during which the meat lay on the sand before it was 
seized and eaten. In some instances the normal movements of 
the animals about the aquarium brought some of them so close 
to the meat that it could be detected by sight. More frequent- 
ly, however, the behavior of the animals indicated that they 
were stimulated by the presence of the meat before it was seen 
by any of them. When the results of this experiment are 
compared with the results of the experiments cited above, it 
becomes apparent that these animals find objects suspended or 
moving in the water much more readily than objects lying on 
the bottom. This fact, as well as the observed behavior of 
the animals, suggests that the olfactory sense plays a much more 
important part in the finding of food when it is in contact with 
the bottom than when it is suspended or moving in the water. 
As determined by examination of their stomach contents, the 
normal food supply of the larvae of Ambystoma tigrinum in 
the habitat in which the animals under observation were tak- 
en, consisted largely of Entomostraca and minute algae. These 
organisms are everywhere present in the water and are not 
secured by active pursuit. On the other hand, the larvae of 
Ambystoma feed also on aquatic insects and insect larvae. The 
latter are found primarily on the bottom. In view of these 
facts the longer interval required to find food on the bottom of 
the aquarium than food suspended or moving in the water, can 
-not be accounted for by the normal feeding habits of the ani- 
