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.
Setae also anchor the worm's body to assist in movement. Muscles : The Earthworm had both circular and longitudinal muscles. These muscles contract, and expand. The expanding movement, is caused by it's circular muscles on each segment, relaxing.