develops from ends during starts during notochord xenopus_anatomy A longitudinal flexible rod of cells that in the embryo forms the supporting axis of the body. It degenerates, beginning anteriorly, at NF stage 46. Its posterior portion is greatly reduced by NF stage 55 and the entire structure is gone by NF stage 65. UBERON:0002328 XAO:0000055 axial mesoderm tissue NF stage 12.5 NF stage 66