Further to David Corfield's post: The diagram below appeared in Frege's _Grundgesetze der Arithmetik_ (vol .1, §172) and illustrates the construction of a mapping that Frege uses to prove that for any finite concept, the objects
falling under it can be well-ordered.

Russell, of course, studied the _Grundgesetze_ closely; perhaps he found inspiration in Frege's figure (if not the almost childish arrows).

[![Scan from Grundgesetze der Arithmetik][1]][1]


  [1]: https://i.sstatic.net/Xwvcw.jpg
  [2]: https://i.sstatic.net/IgSEo.jpg