180 MANTON COPELAND 
eat, so that in a short time they were once more gathered thickly about 
the Squilla. The same test was repeated in another pool, with the 
same aimless wandering and gradual collecting of the snails about the 
Squilla. In the laboratory the Squilla was put into an agate pan 
about sixteen inches square, in which were thirty-five mud-snails. 
The effect was the same as in the pools out of doors. The snails moved 
about actively at first, and in the course of twenty minutes, twenty of 
them had collected on the Squilla and the others had quieted down. 
The Squilla was large and had probably been dead for some time, 
so that its odor or taste was quickly diffused through the pool. Towards 
smaller, live creatures, such as Mya arenaria with a cracked shell, the 
response of Nassa was less rapid, and was not at all definite, unless the 
snail came very near the clam. The definiteness and promptness of 
response seemed to vary somewhat with the nearness of the animal 
to the stimulus, and also with the individual snail. 
This description gives the impression that the food was scented 
by the snails, but that its discovery was perhaps largely a matter 
of chance. In the hope of gaining more detailed information on 
the behavior of Alectrion in the presence of food, the following 
experiment was tried: 
A shallow rectangular glass dish, measuring approximately 
thirty-eight by twenty-three centimeters, was filled with sea 
water. At one end of the dish was placed a ball of cheese cloth 
about three centimeters in diameter, and at the opposite end 
a cheese cloth bag of the same size containing fresh fish (Fundulus) 
meat. Both packets were weighted with a pebble to hold them 
in position. Ten snails were then placed along a line midway 
between the two packets and their behavior noted for one hour. 
That the snails scented the fish when some distance from the 
baited bag was soon made evident. The bottom of the dish was 
slightly concave at the margins, so that the fish juice slowly 
drained toward the two corners nearer the baited bag. The 
snails which moved into the region of the juice extended their 
proboscides, and worked them over the surface of the glass. 
This proboscis reaction, which later was carefully studied and 
found to be characteristic of snails stimulated with dilute food 
materials, often beginning when the animal was several centi- 
meters away from the packet, was particularly marked where the 
juice drained toward the corners of the dish, and sometimes 
occurred in the corners, which were about ten centimeters from 
