OLFACTORY REACTIONS OF MARINE SNAILS 203 
surrounding it with the anterior end of the foot. Oyster juice 
placed in front of the siphon, however, always caused the re- 
tarded area to move forward again at normal speed. 
The results of all the experiments, designed to show how dilute 
tood materials direct the movements of Busycon, indicate that 
the receptor concerned in the reactions is associated with the 
siphon rather than the tentacles or foot. This conclusion is 
supported by other tests to be described. 
When the pipette method of stimulation is used, it is con- 
ceivable that the stream of fluid directed over the siphon tip, 
no matter how carefully applied, may act as a tactile stimulus, 
and thus introduce a factor other than a chemical one, which 
may play a part in determining the response of the snail. That 
such a tactile stimulus alone is incapable of bringing about the 
reactions described is perfectly clear from the failure of the 
animals to respond to sea water, when substituted for oyster 
juice. In order to eliminate a possible tactile influence when 
fluid is forced from a pipette, the soft parts of an oyster were 
tied up in a piece of cheese cloth, and held by a thread over the 
end of the siphon. The two snails tested in this manner became 
very active and were led from the bottom of the aquarium up 
the side without difficulty. They followed the juice slowly 
diffusing from the bag as readily as when it was squirted from a 
pipette. 
The last experiment suggested a similar but more satisfactory 
method for studying the directive influence of olfaction in Busy- 
con, and one which led to some of the most striking results of the 
investigation. Two small sticks, of equal length, were fastened 
to the distal end of the shell siphon with dental wax in such a 
way that they projected beyond the shell and the tip of the 
pallial siphon when fully extended. One stick was directed 
approximately forty-five degrees to the right of the principal 
axis of the siphon, and the other forty-five degrees to the left. 
A piece of oyster was then tied up in cheese cloth, and fastened 
to the free end of one of the sticks three or four centimeters 
from the tip of the shell siphon, whereas a ball of cheese cloth, 
of the same size as the oyster packet, was tied to the end of the 
