Skeletons provide a firm attachment against which muscles can work during movement.
Hydrostatic Skeletons Hydrostatic skeletons consist of fluid held under pressure in a closed body compartment. Found in most cnidarians, flatworms, nematodes and annelids. Control form and movement by using muscles to change the shape of fluid-filled compartments. Provide no protection and could not support a large land animal. Hard encasement deposited on the surface of an animal.