Derived from two embryonic germ layers, the ectoderm and the endoderm.

双胚层的具有两个胚层（外胚层和内胚层）的。

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Derived from two embryonic germ layers, the ectoderm and the endoderm.

双胚层的具有两个胚层（外胚层和内胚层）的。

youdao