We have explained earlier that the presumptive material for the optic vesicles lies in qe eye field in the anterior region of the early neural plate. Experiments on amphibian embryos have displayed that if at this early open neural plate stage this material is cut out and grafted in the flank of another embryo it forms an eye cup displaying that the cells of eye field are already determined to form the eye. This determination is preceded by induction of the ectoderm to form the neural plate by the invagination chordamesoderm throughout gastrulation.
This is followed by the inductive action of the anterior part of chordamesoderm which comes to be underneath the prospective forebrain region of the neural plate, on the anterior part of neural plate. If this mesoderm is eliminated at this stage the eye field does not split and one median eye is formed. Furthermore, if this anterior chordamesoderm is grafted within the prospective hind brain region of the neural plate it induces an eye field in that region. Continued relation with mesoderm is as well essential for further development of the optic vesicle.