OLFACTORY REAC¥FIONS OF MARINE SNAILS 187 
When the foot was stimulated by the use of a pipette plugged 
with cotton, little or no difference in the reaction to the cotton 
flooded with fish juice and to that with sea water could be dis- 
cerned. On stimulating, for example, the posterior tip of the 
foot, it was drawn forward under both conditions, the extent of 
the contraction evidently depending largely on the force of the 
contact. . 
In all these tests upon the snail’s foot, one fact was very 
striking; the animal failed to extend its proboscis in search of 
food, as it characteristically did after fish extract was applied to 
the tentacles. The next problem, therefore, was to determine 
whether stimulation of the tentacles was necessary in order to 
eall forth the proboscis reaction. Accordingly the tentacle 
bases of several snails were cut off as near the head as possible, 
and in all cases, proximal to the eyes. Removing the tentacles 
did not modify in any recognizable way the normal behavior of 
the animals, which, therefore, could be experimented upon shortly 
after the operations. In the absence of the tentacles, the fish 
juice and carmine were applied with a pipette to the lateral 
extensions of the anterior border of the foot already described. 
In fifty tests, twenty upon one animal and ten each upon three 
others, the proboscis reaction took place forty-two times. Only 
two such responses to sea water and carmine occurred in fifty 
tests. 
The fish extract brought forth a very characteristic series of 
movements, which occurred time and time again. The lateral 
process of the foot contracted after stimulation, the moving 
animal then stopped, depressed its siphon into the juice and 
finally extended its proboscis. Often there was no response to 
the sea water and carmine and usually, at the most, but a slight 
contraction of the foot processas the animal continued locomotion. 
The differences in behavior were pronounced. That the pro- 
boscis reaction was not dependent on chemical stimulation of the 
tentacles was clearly shown by these and many other tests, some 
of which will be described. 
The siphon. The movement of the siphon into the fish ex- 
tract was one of the most striking features of the snail’s behavior, 
