n :  a longitudinal flexible rod of cells that in the lowest chordates (as a lancelet or a lamprey) and in the embryos of the higher vertebrates forms the supporting axis of the body, that is almost obliterated in the adult of the higher vertebrates as the bodies of the vertebrae develop, and that arises as an outgrowth from the dorsal lip of the blastopore extending forward between epiblast and hypoblast in the middorsal line no*to*chord*al adj 
 
 
 
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