Final answer:
A hydrostatic skeleton is a type of animal skeletal system formed by the pressure exerted by the aqueous contents of the coelom on surrounding organs.
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 compartment is under hydrostatic pressure because of the fluid and supports the other organs of the organism. This type of skeletal system is found in soft-bodied animals such as sea anemones, earthworms, Cnidaria, and other invertebrates (Figure 29.2).