Expansion and Elongation Migration of Epiblasts to of amni form Endoderm Mesoderm amative Ectoderm 16 days o Expansion of the disk aryngeal Cloacal Notochord mbrane membrane ● Notochord midline rod of mesoderm Yolk sac orientation the germ discExpansion and Elongation •Migration of Epiblasts to form –Endoderm –Mesoderm –Ectoderm •Expansion of the disk •Notochord: -midline rod of mesoderm -orientation the germ disc