OLFACTORY REACTIONS OF MARINE SNAILS DO 
2. Alectrion may crawl with or against a current of water. 
Individuals, which show more or less tendency to move down 
stream, move more often against the current when it contains 
odorous materials derived from food. 
3. Since the stimuli calling forth these reactions are relatively 
dilute chemical ones, the responses are truly olfactory. 
4. It was determined by experimental methods that the 
organ affected by relatively weak chemical stimuli in Alectrion 
was located somewhere within the mantle cavity. The osphra- 
dium is situated on the mantle at the base of the siphon. After 
the osphradium in Busycon was destroyed the snails failed to 
respond to dilute food materials, but a year later, when the 
lamellae of the organ were partly regenerated, the scenting 
responses returned. The osphradium, therefore, is an olfactory 
organ. 
5. When a snail is moving, the siphon, which conducts water 
over the osphradium, to. the gill, is characteristically swung 
from one side to the other. In Alectrion this organ is not 
covered dorsally by an elongated shell siphon, and consequently 
has greater freedom of movement than in Busycon. 
6. When the siphon is directed to one side of its axial position, 
the foot turns in the direction indicated by the siphon, if it 
conducts odorous particles which stimulate the osphradium. 
The snail may be said to be oriented to an odor stream when 
the foot is straightened out and the effective stimulating sub- 
stance is conducted to the osphradium by the siphon in its 
axial position, or when the stimulus is equalized on both sides 
of that position. Accordingly, a snail can be led about an 
aquarium by squirting dilute food extract over the end of the 
siphon when it is pointed in the direction it is desired the 
animal shall take. 
7. When two cheese cloth packets, one containing a piece 
of oyster, are fastened in front of and lateral to the distal end 
of the siphon, one on the right, the other on the left, the snail 
circles toward the source of the strongest odorous substance 
coming from the oyster, that is: to the right when the baited 
packet is on the right of the siphon tip, and to the left when 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25. NO 1 
