It is shown that the ectoderm of the area opaca of chick embryos of the primitive streak stage can react to primitive streak grafts by the formation of an induced neural plate. The conclusion is drawn that the competence to form neural plate is not conferred on ectoderm by the gut endoderm, which determines the formation of the primitive streak.

This work was done while I was in receipt of a part-time grant from the Medical Research Council, and an expenses grant from the Royal Society, for which I should like to make grateful acknowledgment.