Here a photosynthetic flagellate called Euglena deses is dividing.

这里，一种叫做裸藻的光合鞭毛虫裂。

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

所以你知道， 如， 那叫什么，鞭打？

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

例如，人们开始将鞭笞作为赎罪的一种方式。