Final answer:
A hydrostatic skeleton aids in worm movement through muscular contractions that change the shape of the coelom and use fluid pressure to produce movement.
Step-by-step explanation:
A hydrostatic skeleton aids in the movement of a worm by using muscles that surround the coelom. When these muscles contract, they change the shape of the coelom, causing the fluid inside to exert pressure. This pressure then produces movement. For example, earthworms move through waves of muscular contractions called peristalsis. By alternately shortening and lengthening their body, they can extend the anterior end and draw the posterior portion of the body forward.
A hydrostatic skeleton is well-suited for invertebrate organisms such as earthworms, as it allows for efficient movement along solid surfaces.