"A misty English morning the imp hypostasis tickled his brain": strangely, Stephen pairs a most abstruse thought (how Occam imagined that Christ's body could be simultaneously present in different wafers) with a bit of a nursery rhyme from Mother Goose. This incongruous intrusion of a popular ditty in Proteus resembles another in Hades.
A common form of the nursery rhyme goes as follows:
One misty moisty morning,
When cloudy was the weather,
I chanced to meet an old man,
Clothed all in leather.
He began to compliment
And I began to grin,
How do you do, and how do you do,
And how do you do again?
Does this flirtatious, silly meeting somehow cohere with Stephen's thoughts about the Eucharist? It is conceivable that the catchy triplet that ends the rhyme ("How do you do . . . how do you do . . . how do you do again?") has been sounding in his mind as, just before this, he imagines a triplet of sacring bells ("Dringdring! . . . Dringadring! . . . Dringdring!") Or perhaps he is not even consciously thinking of the rhyme.
If he is, it would suggest that Stephen's spirit is becoming lighter and more whimsical as he moves from tortured thoughts about clerics in the previous paragraph to dismissal of his "holy" phase in the next. The irreverent impression created by joining a nursery rhyme to sacred mysteries is repeated in the Glasnevin cemetery when Bloom's thoughts veer into popular music, and he has to remind himself to be more solemn: "The ree the ra the ree the ra the roo. Lord, I mustn't lilt here."