192 MANTON COPELAND 
in the chemical surroundings of a snail may sometimes lead to a 
testing of the environment by this olfactory receptor. That the 
organ sought was the osphradium, which is located on the mantle 
at the base of the siphon, appeared highly probable, but the 
small size of Alectrion made an experimental study of the fune- 
tion of this organ impracticable. ; 
Certain peculiarities of the reactions recorded above will 
be more fully explained in the discussion of the senses of taste 
and smell. 
BUSYCON CANALICULATUM 
In order to investigate further the part played by the siphon 
system in olfaction with special reference to the function of the 
osphradium, and secondly to determine how a snail finds distant 
food, the study of a second species was undertaken. For these 
purposes a whelk, Busycon canaliculatum (Linn.), better known 
by the generic name Sycotypus, was selected, principally on 
account of its large size, but also for its well marked reactions to 
food juices and its general structural resemblance to Alectrion. 
The most conspicuous external morphological difference between 
Alectrion and Busycon is the form of the shell, which in the 
latter species is drawn out anteriorly like an inverted gutter, 
covering dorsally all but the tip of the pallial siphon. This 
shell siphon protects and at the samie time restricts the movement 
of the pallial siphon. 
1. Organs sensitive to food extracts 
When the study of Busycon was first begun, I was unaware 
that the oyster often formed a conspicuous part of its natural 
diet, and the discovery that oyster extract called forth a marked 
response was quite accidental. Food juices procured by grinding 
fish meat in sea water, when squirted in front of a snail, induced 
a reaction involving the protrusion of the proboscis. Accord- 
ingly, the first tests were made with this stimulus. During the 
course of the experiments it happened that some oysters were 
available, and the effect of oyster juice was tried. The resulting 
reaction was so sudden and pronounced that henceforth only 
