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the depression in the primitive node that serves to connect the notochordal canal with the surface ectoderm.
a minute indentation at the anterior end of the primitive groove in the early developing embryo. It lies posterior to the primitive node and probably functions as an opening into the notochordal canal in humans and higher animals and into the neurenteric canal in lower animals.
A minute depression at the anterior end of the primitive groove or streak and immediately posterior to the primitive knot.
See also: pit