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.
Structure. The primitive brain of the earthworm consists of two cerebral ganglia. Sensory nerves leave the brain and run forward to the first segment in the earthworm's body. The nerve cord travels from this first segment to the last.A fibrous sheath surrounds the nerve cord.hile humans and other vertebrates have a spinal column that runs down their back, or dorsal side, earthworms possess a nerve cord consisting of two strands that runs down their belly, or ventral side.