216 MANTON COPELAND 
cauterized animals, which of the four operated upon was in the 
best condition, were placed in an aquarium supplied with running 
sea water. No opportunity of observing them again occurred 
until a year afterwards, when all six were found alive, in fact 
indistinguishable in their behavior from other individuals of the 
species. Upon dropping dilute oyster extract into the water 
in front of their siphons, they responded to it as they had done 
before the osphradia were rendered inoperative. Their move- 
ments were directed by appropriate stimulations with the extract, 
they extended their proboscides in the characteristic manner, and 
again ate oysters which were presented to them when on the 
bottom of the aquarium. The animals were finally anaesthetized 
and examined, and the fact that their osphradia had regenerated 
was clearly apparent. Although regeneration of the organs 
were not complete, several patches of new lamellae covered with 
pigmented epithelium were present in every instance. Thus 
with the reappearance of osphradial tissue the scenting reactions 
returned. 
An analysis of the data recorded above leads, in my opinion, 
to but one conclusion relative to a function of the osphradium. 
The scenting responses of Busycon are dependent on the stimula- 
tion of this organ by materials derived from food, the most dis- 
tinetive feature of which is their diluteness. The osphradium, 
therefore, is an olfactory receptor. 
III. DISCUSSION 
1. Movements resulting from olfactory stimulations 
Some of the results of the experiments described in the pre- 
ceding section of the paper require further explanation or d's- 
cussion. In the first place, however, certain observations upon 
Alectrion should be recorded which were made after the study 
of Busycon was nearing completion. As already mentioned, 
it has been held by Dimon that the mud snail depends almost 
entirely on aimless movements for finding its food in water 
described as quiet. It seemed strange if this were so, since it 
possesses a siphon and osphradium clearly homologous to those 
