Toward the end of Chapter 8, Nick describes Gatsby as existing in "A new world, material without being real, where poor ghosts, breathing dreams like air drifted fortuitously about . . . " The quote refers to two ghosts. Who are they?

The complete question is here.

Toward the end of Chapter 8, Nick describes Gatsby as existing in "A new world, material without being real, where poor ghosts, breathing dreams like air drifted fortuitously about . . . like that ashen, fantastic figure gliding toward him through the amorphous trees." The quote refers to two ghosts. Who are they?