Both snails and slugs have gel-like bodies, travel on a trail of slime and have four tentacles – to on the top of the head with eyes on the end and two below the head for sensory purposes. The main difference is the most obvious one: The slug doesn’t carry a shell, although some may have plate on top of the mantle, which is just behind the head.
Now you know!!!
Taken from The Progressive Farmer June/July 2006