Diogenes' masturbatory episode is referred to darkly by
Bertrand Russell in his tome
A History Of Western Philosophy, in the following passage:
The cynics thought that one should be without shame, and Diogenes would have none of it, wishing to be in all things like a dog; yet even he, after one attempt, abandoned, in practice, this extreme of shamelessness.
(The word '
cynic' is derived from the greek for 'dog'.)
Diogenes is also known for wandering around Athens carrying a lit lantern, in bright daylight. When challenged as to his purpose in this, he's said to have replied: "I'm looking for an honest man."
Thus, he's often depicted alongside a dog, and holding a lantern.