All chordates have a notochord present in the embryonic stage. In Tunicates, the notochord is present only in the larval stage, being completely absent in the adult animal. Urochordates, like Herdmania have notochord and nerve cord present only in tail. Tadpole undergoes retrogressive metamorphosis and notochord and nerve cord is absent in adults, which is lost during metamorphosis. In vertebrates the notochord develops into the vertebral column, becoming vertebrae and the intervertebral discs the centre of which retains a structure similar to the original notochord.