Haines suggests that he might publish a collection of Stephen’s sayings, but Stephen impertinently suggests he’ll participate if he stands to make any money by it. He thinks to himself how Mulligan’s and Haines’ habit of bathing is an attempt to cleanse themselves of more than just dirt.
In the first panel of this page, there’s a kind of exchange between Haines’ dialogue and Stephen’s internal monologue. Of course, what Stephen is thinking to himself (in the dark boxes) is harder to understand than what Haines is saying out loud. “They wash and tub and scrub” refers back to Mulligan’s teasing about Stephen’s infrequent bathing (check the last page), which Stephen also associates with Lady Macbeth’s scrubbing.
“Agenbite of Inwit” is a little more obscure. It’s a Middle English phrase that means (again according to Professor Gifford) “remorse of conscience.” When you think about it, it makes wonderful sense. Your inner wits bite you. again.
The kick under the table is Mulligan kicking Stephen, so as to get him to perform his Shakespeare theory and close the deal on Haines’ support. Or at least to get Haines to buy a few round of drinks. But Stephen does not want to play–apparently he’s in no mood, and since he’s getting paid today he doesn’t need Haines’ help. So he does a decidedly un-English thing and puts his desire to be paid for his work out in plain view.