Before revision: In Xenopus laevis , the specification of the three germ layers (endoderm, mesoderm and ectoderm) occurs at the blastula stage.Heasman, J., Quarmby, J., and Wylie, C.C.
After revision: (a common model system for the human)In Xenopus laevis , the specification of the three germ layers (endoderm, mesoderm and ectoderm) occurs at the blastula stage.Heasman, J., Quarmby, J., and Wylie, C.C.