The juxtaposition between the complicated and ancient theory of metempsychosis and the trashy novel Molly has been reading is classic Joyce; he loves to play around with the contrast between highfalutin ideas and the flotsam and jetsam of popular culture. Bloom smiling at Molly’s “mocking eye” is Joyce’s way of having his main character get that joke; it’s also a moment of affection and a prompt for another memory that doesn’t quite get filled in: Dolphin’s Barn is an area just outside Dublin where Molly was living with her father “Major” Tweedy when she first met Bloom (and, incidentally, where Dublin’s official Jewish cemetery is located). (Memories of Molly’s first encounter with Boylan, at a dance, show up later, too.)
Bloom takes the trashy novel, and its illustration fills the center of the page. Ruby: The Pride of the Ring is Joyce’s reworking of an actual book title, Ruby. A Novel. Founded on the Life of a Circus Girl (1889); the novel was about the harsh servitude of circus life and, as Gifford points out, was meant to spark reform. The illustration depicts an actual scene in the novel, where a circus master works the victimized Ruby to death. In Joyce’s hands, the reform impulse is turned into something more salacious, and the image looks a little like rape (perhaps echoing the duet between Don Giovanni and Zerlina, too). Bloom thinks about the circus as he regards the illustration, while also trying to figure out a way to define metempsychosis for Molly.
Incidentally, and probably not surprisingly, the word “metempsychosis” does not appear anywhere in the real Ruby.