Notochord
In anatomy, the notochord is a flexible rod formed of a material similar to cartilage. If a species has a notochord at any stage of its life cycle, it is, by definition, a chordate. In vertebrates, the notochord develops into the vertebral column[citation needed]. The notochord lies along the anteroposterior ("head to tail") axis, is usually closer to the dorsal than the ventral surface of the animal, and is composed of cells derived from the mesoderm.
Notochord-1