I wonder if ἐφ’ ὧν refers to τὰ νοητὰ as you said or to τοῖς αἰσθη-
τοῖς εἴδεσίν. I don’t quite understand the intended meaning here so I’ll leave it to others.
In any case, the preposition ἐπί is elided (i.e., its final vowel is removed) before aspirated
words such as the gen. pl. relative pronoun ὧν, transforming the consonant π into φ.
No, I don’t mean the aphostophy mark attached to eph’.
Do you see in your text an apostophy mark at the end of eklimpanei ?
What confuses me is that.
I’m sorry not writing in Greek character.
But since I am Japanese, the instruction page on this site how to set one’s computer to type in Greek character, is difficult.
So I have postponed the setting operation, till some day.
You don"t have to change your computer settings. You can use this site to type using English characters – they will be automatically converted into Greek: http://users.ox.ac.uk/~tayl0010/polytonic-greek-inputter.html
It also generally helps if you can give the author, work and chapter for such questions – sometimes context helps, and it’s easier for us to check if we know what text the Greek is from.