OLFACTORY REACTIONS OF MARINE SNAILS ALS 
When the snail was held in the hand, or when it was on the side 
of the aquarium with its head at the surface of the water, the 
oyster could be laid upon the skin of the foot and head region 
with little or no diminution in the strength of its stimulating 
materials. The point is well illustrated by the following case: 
One of the snails, which was moving on the bottom of the aqua- 
rium, could not be induced to take a piece of oyster which was 
placed beneath its head. The animal was removed from the 
water and the same piece, by that time well rinsed, dropped on 
the under surface of the head. Again there was no response. 
- Finally a fresh juicy piece was taken from a dish and presented 
to the snail in the same manner. It was taken into the mouth 
instantly. 
The last experiment supports the view that the reactions to 
oysters are brought about by chemical rather than tactile stimu- 
lation. In order to gain more information on this point, a few 
tests were made as follows: A piece of cotton soaked in sea water 
was placed against, or close to the under side of the head and the 
effect recorded. The cotten was then soaked in oyster extract 
and returned to the same region, and the reaction compared 
with the preceding one. The snails were held in the hand, or 
were resting at the surface of the water when the tests were 
made. In ten trials, including the five animals, the cotton and 
oyster juice always caused a flaring of the false mouth, or a 
protrusion of the proboscis. There was no visible reaction to 
the cotton soaked in sea water except in two trials fifty minutes 
apart on the same individual, when the proboscis was thrust out. 
No attempt was made, however, to seize the cotton, whereas 
the snail plainly tried to take the cotton soaked in oyster juice 
into its mouth in the two succeeding trials. In three other tests 
made upon this animal at later times no reaction to the cotton 
and sea water occurred. Excessive hunger may have been a 
factor in starting the feeding response in the two instances cited. 
It is clear that a chemical stimulating agent is the appropriate 
one for bringing about the reaction to food. 
After concluding the experimental work upon these five 
snails with non-functional osphradia they, with one of the 
