芝麻籽大小的小蝌蚪现在已经分成了三层：外胚层、中胚层和内胚层。

The little tadpole about the size of a sesame seed is now made up of three layers: the ectoderm mesoderm and endoderm.

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芝麻籽大小的小蝌蚪现在已经分成了三层：外胚层、中胚层和内胚层。

The little tadpole, about the size of a sesame seed, is now made up of three layers: the ectoderm, mesoderm and endoderm.

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当一个生物产生时，胚胎将形成三个胚层外胚层、内胚层和中胚层，然后再由这些胚层形成机体的组织和器官。

When an animal develops, embryos form three cellular or germ layers - ectoderm, endoderm and mesoderm - which then go on to form the body's organs and tissues.

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