Most authors position the notochordal process in-between the endoderm and ectoderm, which is the position of the definitive notochord. These cells would then become incorporated into the endoderm, forming the notochordal plate and subsequently would detach from the endoderm to form the definitive notochord.

Is notochord present in endoderm?

Embryos of modern vertebrates form transient notochord structures during gastrulation. The notochord is found ventral to the neural tube. ... Initially, it exists between the neural tube and the endoderm of the yolk-sac; soon, the notochord becomes separated from them by the mesoderm, which grows medially and surrounds it.

What produces the notochord?

The notochord derives during gastrulation (infolding of the blastula, or early embryo) from cells that migrate anteriorly in the midline between the hypoblast and the epiblast (inner and outer layers of the blastula). These cells coalesce immediately beneath the developing central nervous system.