Here a photosynthetic flagellate called Euglena deses is dividing.

在这里，一种叫做裸合毛虫正在分裂。

So you know, if ever I feel like, what is that called, flagellating?

所以你知道， 如果我想， 那叫什么，？

For instance, people started flagellating as a way to atone for their  sins.

例如，人们开始将笞作为赎罪一种方式。