immediate transformation of germ layer germ layer 胚层 mesoderm mesoderm 中胚层 The middle germ layer of the embryo, between the endoderm and ectoderm. embryonic mesoderm entire mesoderm mesodermal mantle The middle germ layer of the embryo, between the endoderm and ectoderm. embryonic mesoderm entire mesoderm mesodermal mantle 中胚层套膜 整个中胚层 胚胎中胚层 胚胎的中间胚层，在内胚层和外胚层之间。 presumptive mesoderm mesoderm mesoderm 中胚层 The middle germ layer of the embryo, between the endoderm and ectoderm. embryonic mesoderm entire mesoderm mesodermal mantle The middle germ layer of the embryo, between the endoderm and ectoderm. embryonic mesoderm entire mesoderm mesodermal mantle 中胚层套膜 整个中胚层 胚胎中胚层 胚胎的中间胚层，在内胚层和外胚层之间。