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.
dorsal blood vessel. The dorsal blood vessel is an important part of an earthworm's circulatory system as well as its respiratory system. Since an earthworm has neither lungs nor gills, oxygen must be absorbed through its skin and passed onto the bloodstream through the dorsal blood vessel.