A slug does not have a traditional nose, but rather a pair of tentacles that it uses to smell. A slug also has two other tentacles that contain eyeballs on the tips.
The tentacles used for smelling are smaller than the pair used for sight. The tentacles for scent are on a slug's face, while the ones for sight are positioned on the top of the head. The tentacles designed for smelling each contain a pair of nostrils. A common misconception about slugs is that they have four noses. The number of tentacles is the underlying reason for this misconception.