It's harder to find, they're more limited numbers, and in general, more difficult until eventually down this pathway you have fully differentiated cells, cells that are fully mature and performing the function of the mature organ.

不过找起来更困难,因为它们数量稀少而且通常很难定位,在分化的终末阶段,你可以看到完全分化的细胞,这些细胞完全成熟,在成熟的器官中发挥功能

耶鲁公开课 - 生物医学工程探索课程节选

One answer, and it's the one that is most widely believed among Greek scholars, is that the growth of population that we have mentioned in connection with the rise of the polis is still working once the polis comes into form.

原因之一是,这个原因是被广大古希腊学者们所接受的,那就是,人口的增长与城邦的数量,在城邦兴起的阶段还是基本一致的

耶鲁公开课 - 古希腊历史简介课程节选