Animals like us have our guts and circulatory system on our belly side and our nerve cords along our backs.

像我们这样的动物在腹部有我们的内脏和循环系统，在背部有我们的神经索。

And to seal the deal, they absorb all of those useful features that let them move around – the eye, the nerve cord, and – you guessed it – the brain.

为了成功，它们吸收了所有让它们能够移动的有用特征——眼睛、神经索，还有——你猜对了——大脑。