Does a worm have a exoskeleton?

A hydrostatic skeleton or hydroskeleton is a structure found in many cold-blooded organisms and soft-bodied animals consisting of a fluid-filled cavity, the coelom, surrounded by muscles. Some examples are soft bodied animals such as sea anemones and earthworms. Hydrostatic skeletons have a role in the locomotion of echinoderms (starfish, sea urchins), cnidarians (jellyfish), annelids (earthworms), nematodes, and other invertebrates. They have some similarities to muscular hydrostats.