The spinal cord begins at the occipital bone and extends down to the space between the first and second lumbar vertebrae; it does not extend the entire length of the vertebral column.
Earthworms are invertebrates, lacking a skeleton. To support and shape the body, they are filled with coelomic fluid. Earthworms sometimes appear to have a belt or saddle around their bodies; this is a clitelum, a structure containing maturing eggs.
Earthworm-Muscular System. The earthworm has two muscles which it uses for locomotion, both of which run the whole length of the worm's body. These two muscles are circular muscles and longitudinal muscles (Musurca).The longitudinal muscles are the inner layer of the muscular series and cradle the coelom, the innards of the earthworm (Noble).When the circular muscles are contracted, the diameter of the body is reduced, making the worm thin.hen the longitudinal muscles are contracted, the length of the body is reduced, making the worm short. So, if an earthworm is short and thin, which is a common reaction, both types of their muscles are contracted.