英语语法分析

Then they amputated a small piece from each flatworm.

然后他们把每个涡虫切成小块。

The flatworm relies upon a population of stem cells to accomplish this remarkable feat;

扁形虫（涡虫是一种扁形虫）要靠大量的干细胞才能完成这种非凡的技艺；

After all, the flatworm planaria does just fine with eyes that are arguably not as good.

从上可知，扁形涡虫的眼睛比理论上要好得多。