原腸胚 嚢胚
double-walled stage of the embryo resulting from invagination of the blastula the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm
胞胚の陥入によって、胎児が二重の壁で囲まれる段階 外側の細胞層は外胚葉で、内側の細胞層は中胚葉と内胚葉に分化する