translation.en: And he's looking at them by looking at the embryo genesis of birds and actually looking at how they develop, and he's interested in how birds actually lost their tail.
translation.zh: 他研究返祖 是通过研究鸟的胚胎发育 看它们是怎么发育的 他对鸟类的尾巴是怎么消失的感兴趣