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.
Earthworms are simultaneous hermaphrodites, having both male and female reproductive organs. A simultaneous (or synchronous) hermaphrodite (or homogamous) is an adult organism that has both male and female sexual organs at the same time. Self-fertilization often occurs.