notochord

A flexible rodlike structure that is present in the embryos of all chordates and in the adult forms of certain groups, such as the lancelets and hagfishes. The notochord develops into the spinal column in most vertebrates.

A vestigial structure, representing a very ancient form of alimentary canal not in itself a part of the skeleton.

The chorda dorsalis or primitive backbone: a fibrocellular or cartilaginous rod-like structure which is developed in vertebrates as the basis of the future spinal column, and about which the bodies of the future vertebræ are formed.

An elastic cartilagelike rod which is developed beneath the medullary groove in the vertebrate embryo, and constitutes the primitive axial skeleton around which the centra of the vertebræ and the posterior part of the base of the skull are developed; the chorda dorsalis. See Illust. of ectoderm.

A flexible rodlike structure that forms the main support of the body in the lowest chordates; a primitive spine

A similar structure found in the embryos of vertebrates from which the spine develops

a flexible rodlike structure that forms the supporting axis of the body in the lowest chordates and lowest vertebrates and in embryos of higher vertebrates