OLFACTORY REACTIONS OF MARINE SNAILS 181 
the tish meat. The proboscis was extended farther when the 
snail approached the source of the stimulating material closely, 
and two or three of them climbed upon the bag in their attempts 
to secure the food. Sometimes the snail’s siphon was brought 
within one or two millimeters of the bag before the proboscis 
was protruded. This was especially true when the bag was 
approached from the center of the dish toward which less juice 
was spreading. Eight of the ten individuals came near to the 
bag and extended their proboscides, the latter reaction always 
occurring ‘before the siphon touched the cheese cloth. No 
behavior of this sort was observed at the opposite end of the 
dish, although six individuals came into contact with the un- 
baited packet, touching it ten times during the hour. They 
always moved away from it and no proboscis activity took place. 
Other experiments of a similar kind, varying somewhat in 
details, were carried out, and gave essentially the same results. 
That dilute materials emanating from fish meat stimulate 
Alectrion and cause the animal to thrust its proboscis, in short, 
that the snail scents distant food, was clearly demonstrated. 
Whether the final discovery of the food is the result of chance 
movements, or of some directive influence of olfaction, is a prob- 
lem which will be discussed later, particularly in connection with 
the reactions of Busycon. 
The responses of Alectrion to distant food in a current of water 
were next investigated. Dimon (705) describes the activities 
of the mud snail when in a stream containing food juices which 
flowed down a beach, and concludes that “if a current flows 
from the food to a snail, the animal will crawl up toward the 
food.’ The same author also finds, however, that the snail 
“shows a tendency either to move against a moderately strong 
current, or to orient itself when at rest with its head pointing 
against the current.’’ The reader, therefore, is left somewhat 
in doubt as to the significance of the snail’s movements against 
the current in the first instance, and may ask: Were they affected 
by the presence of food up the stream? 
In order to determine whether food juices added to the water 
caused Alectrion to move more frequently against the current, 
