1. 1. A long-term learning phenomenon in the tentacle of Helix pomatia has been observed.

 

2. 2. Repeated mechanical stimulation of the optic tentacle led to habituation of the associated withdrawal-extension action pattern whereas repeated combined mechanical and electrical stimulation potentiated the reflex.

3. 3. The potentiation was present 40 days after four sessions of stimulations. Sessions spaced with proportionally increasing intervals were more effective than massed training. Puromycin (125 mg/ml) blocked 80% of protein synthesis as well as the long-term but not the short-term retention of potentiation.

4. 4. Contrary to observations in other preparations, the amount of water soluble proteins, notably S-100, was not affected by learning. Injections in vivo of and exposure of brain in vitro to S-100 had no effect on learning or a variety of brain potentials.