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.
A roundworm has no skeleton. Digestion: A roundworm has a definite digestive system that runs the length of their bodies. It has a mouth, pharynx, intestine and anus. Many are parasites and live off other animals and plants. Nervous: A roundworm has two nerve cords that transmit impulses in the roundworm. Circulation: A roundworm has no heart or formal blood vessels. Respiration: A roundworm has no formal respiratory system. Reproduction: A roundworm reproduces sexually. The female has an ovary, holds eggs in an oviduct and then passes them to the uterus, where they are fertilized. The male has sperm cells are made in the testis and stored in the vas deferens. When it is time to reproduce, the sperm cells pass through the spicule.