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.
One of the most interesting aspects of earthworms is their sexuality. Earthworms are simultaneous hermaphrodites, meaning worms have both male and female reproductive organs. During sexual intercourse among earthworms, both sets of sex organs are used by both worms. If all goes well, the eggs of both of the mates become fertilized.