Final answer:
A hydrostatic skeleton is a fluid-filled compartment that supports and provides movement to soft-bodied animals. Muscles surrounding the fluid-filled compartment contract to produce movement.
Step-by-step explanation:
A hydrostatic skeleton is a skeleton formed by a fluid-filled compartment within the body, called the coelom. The organs of the coelom are supported by the aqueous fluid, which also resists external compression. This type of skeletal system is found in soft-bodied animals such as sea anemones, earthworms, and other invertebrates. Movement in a hydrostatic skeleton is provided by muscles that surround the coelom. The muscles contract to change the shape of the coelom, which produces movement. For example, earthworms move by waves of muscular contractions called peristalsis.