The AA. investigated the innervation of the foot of mussel Mytilus gallo-provincialis Lam. through specific histological techniques. They examined the muscular, glandular and subepithelial nerve endings. Both the nerve trunks (pedal nerves) originating from the pedal ganglia enter the foot from basal side; they branch out and form nerve plexuses. Within the muscular and glandular system and in the subepithelial zone, the AA. found fine nerve endings of possible sensorial function. No investigation on this field was found in the literature up to the present time. The relationships between the behaviour and the innervation are discussed.