The scorpion

This answer and more can be found on the gradesaver website. Just follow the link at the bottom!

Scorpion

One of the important, but subtle, symbols within the first part of the story is the scorpion that the chief mate finds in his cabin. In the story, the mysterious creature causes the mate much speculation as why it chose his particular cabin and drowned itself in his inkwell. As the story progresses, the same questions can be applied to Leggatt, as the scorpion in the mate's cabin and Leggatt in the Captain's cabin are similar - they are dangerous, they come from places that are far removed from the boat, and they hide in cabins. The scorpion, therefore, symbolizes the future intrusion of Leggatt on the ship and within the captain's cabin. The mate's speculation concerning the scorpion, however, can also be applied to Leggatt - it is not that he has chosen specifically the captain, but he is a more universal symbol of the subconscious and "darker self" that plagues everyone, everywhere.