Figure 1.

Sample trails left by test Euglandina during odor learning experiments. The movements of the snails are tracked by visualizing the mucus trails with charcoal. (A, B) Odorant-soaked cotton swabs—location marked with (s)—were placed at one end of a transparency sheet and test snails were placed at the other end. In A, the snail approached very close to the swab, while in B the snail moved opposite to the swab. (C, D) An odorant-soaked swab—location marked with (s)—was placed behind the snails. In C, the snail turned to approach the swab, and the trial was scored as “attracted.” In D, the snail did not turn to approach the swab within 10 cm of the initial location so the trial was scored as “not attracted.” (E, F), Following an artificial trail of odorant (at location of pen line). Snails initial location at left corner of the sheet. In E, the test snail was scored as following the trail. In F, the test snail was scored as not following. The pen lines to mark the location of the swabs, the odorant trails and the “attracted/not attracted” line were all added after the conclusion of the behavioral experiment.