But the ape, seeing this, was indignant: for the man seemed to him to be ungrateful and impudent, seeing that he (say ‘who,’ ὅστις) having found the water by reason of him[1] (reflexive) was not (say ‘is not’) willing to give him any share.
[1] See §17
Answer from key:
ὁ δὲ πίθηκος τοῦτο ἰδὼν ἐσχετλίαζε· ἀχάριστος γὰρ ἔδοξεν εἶναι καὶ ἀναιδὴς ὁ ἀνήρ, ὅστις δι’ αὑτοῦ εὑρὼν τὸ ὕδωρ ὀὐδὲν θέλει μεταδοῦναι.
Section §17: ‘Him’ Reflexive
It should be, however, observed, that in English we do not always say ‘himself,’ but often simply ‘him’ (‘her,’ ‘it,’ etc.), even where the Pronoun is really reflexive. Thus:–
They knew he was hostile to them.
[them is relexive = themselves]
ᾔδεσαν αὐτὸν σφίσιν ἐχθρὸν ὄντα.He said it was his cloak
[his = of himself.]
ἔφη ἑαυτοῦ εἶναι τὸ ἱμάτιον.He took it away with him.
ἀπέφερε μεθ’ ἑαυτοῦ.
αὑτοῦ (ἑαυτοῦ) makes sense to me here, while αὐτοῦ or ἐκείνου would be confusing, but I’m not sure that I could explain it. The man seems to be the subject in that part of the phrase.