Worm Anatomy 101
The worm's body is the same on both sides of the dorsal midline. This is known as bilateral symmetry.
The worm has a true body cavity called a coelom (SEE-LUM)
The worm's body is a long tube with in an equally long tube. The hollow digestive tube or alimentary canal, is suspended within and does not touch the body wall. The space between the outer surface of the digestive tube and the inner surface of the wall tube is the coelum. This cavity is present in some form in all multi-celled animals, but is not so easy to observe.
Worms have a moist body covering called a cuticle. Under the epidermis layer the epithelial cells contain mucus glands to keep the cuticle soft and pliable. The epidermis also contains sensory cells that orient the worm to its environment.
The body wall is mostly muscle. There are circular muscles which can reduce the diameter of the worm's body and longitudinal muscles that relax and contact to activate crawling.
The worm has a fleshy bumper at the front end called the prostominum. This juts out over the mouth and shields of the worm as it moves forward.