200 MANTON COPELAND ; 
ture leading into the sac surrounding the proboscis was seen to 
flare, a reaction often noted when an animal was responding to 
an olfactory stimulus, and the proboscis was not fully extended. 
Upon arriving at the surface of the water, it was offered a piece 
of oyster which it ate. In cases where a snail was successfully 
directed from the bottom to the side of the aquarium, the pro- 
cedure and reactions were much the same as in this instance. 
In order to show, on the other hand, that a snail could not be 
directed upward until after the free end of the siphon was raised, 
another test may be described. After appropriate stimulations, 
the snail moved to the side of the aquarium, but then failed to 
lift its siphon. The oyster extract squirted over the siphon tip 
caused the animal to move parallel to the glass side, the right 
border of the foot being actually on it. Whenever the end of 
the siphon was slightly raised the stimulating material was 
applied, and finally the whole foot was fastened to the glass. 
In this position the siphon was moved very little, and stimulation 
resulted only in locomotion along the side of the aquarium close 
to and parallel with the bottom. ‘The proboscis was extended, 
showing conclusively that the animal was scenting food juices. 
It eventually arrived at the end of the aquarium where the siphon 
was swung to the right. Upon applying the stimulus with the 
siphon pointing upward, the foot turned in the same direction 
and there was no further difficulty in leading the animal to the 
surface. 
A third case illustrates how a snail can be made to circle 
while crawling on a vertical surface. The animal tested was 
resting by the side of the aquarium, the left surface of the end 
of the siphon in contact with the glass. Sea water squirted into 
the distal aperture of the siphon produced no reaction, but oyster 
juice caused locomotion. The latter was then liberated over 
the end of the organ when it was raised on the glass, and although 
it was swung off the side to the right once or twice, the foot 
turned sharply to the left, and the snail began crawling upward 
in the direction of the extract, as in the other instances recorded. 
In its upward course it moved slightly to the right of a vertical 
line, and the siphon was swung to the right and left in the usual 
