摘要: Abstract The small freshwater pulmonate Physa has to surface at intervals replenish its air bubble. If kept in a conical flask with glass Y-tube giving access the above it, an individual snail will tend go same side of Y great regularity. Rotation maze shows that orients itself respect cues within tube. Further experiments (changing water tube, scrubbing out swapping tubes between individuals) show animals lay trails and follow these successive runs surface; effect blocking ‘preferred’ arm is reported some detail. It can be shown not only responds laid by other individuals, but also able determine direction which individuals were going; polarized trail lasts about 30 min. Preliminary seashore prosobranchs Monodonta Littorina too are followed subsequent individuals. phenomenon trailfollowing discussed relation homing predation, interpretation on learning gastropods general.