This tube is the cartilaginous tube spoken of above and is known as the cartilaginous sheath of the notochord.
This structure is called the notochord (a string down the back).
In fig. 7b, the most anterior of the two, the notochord has become quite separated from the hypoblast.
Nevertheless, traces of the notochord persist in the back-bone of these fishes.
The notochord is unconstricted, but the neural and haemal arches are well-developed, and the neural spines are long and slender.
The notochord is restricted and replaced by ossified vertebræ.
These are a pair of chitinous rods which lie ventral to the notochord and in the collar region unite to form a single mass.
The notochord is persistent and unconstricted, and the limbs are archipterygia.
The notochord would almost appear to arise as a third median and dorsal diverticulum of the archenteron (fig. 180 ch).
Ridge of hypoblast, which will become separated off as the notochord.
1848, coined in English by English anatomist Sir Richard Owen (1804-1892) from chord + comb. form of Greek noton "back," from PIE *not- "buttock, back" (cf. Latin natis "buttock," sopurce of Italian, Spanish nalga, Old French nache "buttock, butt").
notochord no·to·chord (nō'tə-kôrd')
A flexible rodlike structure that forms the main support of the body in the lowest chordates; a primitive backbone.
A similar structure in embryos of higher vertebrates, from which the spinal column develops.
A flexible rodlike structure that forms the main support of the body in all chordates during some stage of their development. In vertebrates, the notochord develops into a true backbone in the embryonic phase. Primitive chordates, such as lancelets and tunicates, retain a notochord throughout their lives.