They are derived from the area of the neural plate anterior to primitive knot.

The region anterior to the primitive knot can be generally referred to as the neural plate.

Signals for the anterior/posterior axis come from primitive knot.

The primitive knot (or primitive node) is the organizer for gastrulation in vertebrates.

The primitive knot migrates posteriorly as gastrulation proceeds, eventually being absorbed into the tail bud.

In the mathematical theory of knots, a Berge knot or doubly primitive knot is any member of a particular family of knots in the 3-sphere.

Drawing upon the recent work of Warren H. Lewis and Ethel Browne Harvey, he turned his skills to the gastrula, grafting a "field" of cells (the Primitive knot) from one embryo onto another.

In chick development, the primitive knot starts as a regional knot of cells that forms on the blastodisc immediately anterior to where the outer layer of cells will begin to migrate inwards - an area known as the primitive streak.