OLFACTORY REACTIONS OF MARINE’ SNAILS 205 
(trial four) was there a failure in this response, and in that case 
the snail started to turn to the left before circling to the right, 
and behaved in a sluggish manner. In trial one the snail turned 
to the right after circling one hundred and eighty degrees to the 
left. In most instances the animals hit the side of the aquarium 
after turning about ninety degrees, but in trials one, nine and 
ten they circled one hundred and eighty degrees or over without 
meeting any obstruction. There seemed to be some tendency 
shown to turn more sharply when circling to the left. 
Trial nine was so remarkable that it deserves special descrip- 
tion. The bag containing oyster meat was tied to the left stick, 
and the snail immediately started forward turning to the left 
and rendering evidence that food was scented by exhibiting 
vigorous sweeps of its siphon. The tentacles curved downward, 
their tips now and then touching the bottom of the aquarium. 
Continuing to the left, the animal completed the first circle in 
four minutes without hitting the sides of the aquarium. After 
moving three-quarters of a second circle, it encountered the side, 
but swung clear and continued its course to the left, finally 
completing two and a half circles in eight minutes. It then came 
in contact with the aquarium side and lifted its siphon, thus 
bringing the packets above the end of the organ. Still following 
the scent, the snail crawled up the side of the aquarium, eighteen 
centimeters high, until both packets were actually lifted above 
the surface of the water. In this position the animal was fed 
with a piece of oyster. 
A number of tests were made in order to determine whether 
the behavior of the snails just described could be interpreted in 
any other way than as responses to chemical stimulations. 
Animal number five (without tentacles) was observed while 
carrying sticks supporting two cheese cloth packets, neither one 
of which contained oyster meat. After several trials it became 
evident that the presence of the apparatus on the shell siphon did 
not produce any unusual behavior. There were no marked 
circling movements shown, and when slight deviation from a 
straight course took place it was as often in one direction as the 
other. When the animal, still carrying the packets, was stimu- 
