226 MANTON COPELAND 
it is on the opposite side. Similar circus movements take 
place when the siphon is fastened to one side of its axial posi- 
tion, and oyster extract is squirted into the water in front, and 
to the right and left of the snail. 
8. The snails do not tind food by coming upon it accidentally, 
but are directed to it by movements brought about through 
stimulations of the oifactory organ with odorous substances 
conducted to the receptor in varying concentrations by the 
moving siphon. By means of an olfactory apparatus, con- 
sisting of a single organ of smell associated with a siphon ter- 
minating in a shifting ‘nostril,’ for sampling the surrounding 
water and its contents, the snail is as successfully directed 
toward distant food as an animal which, like the dogfish, 
possesses paired olfactory organs and fixed nostrils. 
9. All the skin surfaces of the snails which were tested were 
found to be more or less sensitive to the more concentrated 
stimuli derived from food. 
10. When fish extract is applied in its full strength to a 
tentacle or anterior foot process of a moving Alectrion, the 
animal stops and turns its siphon into the stimulating substance. 
Busycon deprived of its osphradium often fails to give evidence 
of sensing food which is placed near it, or perhaps in contact 
with it. When, however, the snail is removed from the water, 
or is resting on the side of an aquarium at the surface of the 
water, it characteristically protrudes its proboscis and takes 
food placed on the anterior end of the foot, or in contact with 
the head and tentacles. These positive reactions of Alectrion 
and Busycon are the effects of stimulations by relatively 
strong food solutions and, therefore, are gustatory. The 
principal external receptive areas for taste stimuli appear to 
be the tentacles, the anterior end of the foot and the under 
part of the head. 
11. The snails obtain food through the senses of smell and 
taste, but the latter is effective only in the last stages of its 
procurement. There is no evidence that the eyes play a part 
in the reactions to food, but the tactile sense may do so under 
some circumstances. 
