Worm Farms: How Worms Move
Muscles and the setae are the worms most important anatomy parts for moving. There are muscles that go both circularly around the body and length ways down the body.
To make this really simple; worms move along by extending the anterior (front end), taking hold using their front setae (bristles) then retracting the setae at the prosterior (back end) and pulling their prosterior to their anterior.