OLFACTORY REACTIONS OF MARINE SNAILS 185 
means of a finely drawn out pipette, a marked reaction followed. 
The tip of the tentacle coiled rather violently, the animal stopped, 
the siphon was swung into the stimulating material and the 
proboscis extended and worked over the bottom of the glass 
dish in which the tests were made. Numerous animals were 
tested, and although considerable individual variation in respect 
to sensitiveness to the stimulus was noted, the reactions were 
remarkably constant, as the following responses of five snails 
will show. Sea water mixed with carmine was always applied 
with a special pipette to the tentacle before the fish juice in 
order to make sure that the reactions observed were due to chemi- 
cal rather than tactile stimulation. The snail was moving when 
the test was made, and at least a minute elapsed between each 
trial with the fish juice. The material was applied five times 
to the right tentacle, and then five times to the left one, and 
care was taken to have the snail in water free from the stimulat- 
ing substance when the test occurred. In fifty trials, ten with 
each individual, there were forty-seven reactions as described 
above. One failure to respond was noted, and two cases where the 
proboscis was extended but locomotion continued. The animals 
scented the juice, therefore, forty-nine times in fifty trials. 
To sea water and carmine the snails usually responded, if at 
all, by twitching or coiling slightly the tips of their tentacles 
without cessation of locomotion. With the exception of one 
doubtful case, the proboscis was protruded but three times in 
the fifty trials, and then without the animal stopping as it 
characteristically did when stimulated with fish juice. 
Another method for comparing the effect of a pure tactile 
stimulus with that of one accompanied by a chemical stimulus was 
as follows: A small piece of cotton was rolled into a ball and 
placed in the open end of a pipette. Some filtered Fundulus 
extract was then put into the pipette back of the cotton. By 
exerting slight pressure on the bulb it was possible to flood 
the cotton with juice, which then could be applied locally to 
any part of the snail’s body. A pipette plugged with cotton and 
holding sea water was used in a similar way when a pure tactile 
stimulus was required. 
