In the original edition and subsequent, until 1961, the S of the first chapter is a bit higher as well as the M in the 2nd. and the P in the 3rd.chapter, all full-page and a "dot" at the end of episode 17.

They have the function of indicating:

S = Subject = Stephen Dedallus
M = Middle = Molly Bloom
P = Predicate = Poldy's = Lopold Bbloom

Dot = . = Q E D = quod erat demonstandum, which means "which had to be demonstrated" or "it has been proved".

It was a medieval pedagogyl S-M-P indicating the order of cognitive thought that should be learned.

It suggested a logical narrative structure that the reader could see, but the fictional characters completely ignored.

S + M = P or, the "X" of the question is M, Nora Barnacle or Molly...

More information on Ulysses Annotated by Don Gifford, pg 12, under S.

The similarity between Joyce's Ulysses and Homer is more of a structural correlation, and is the same that is used by scholars of the text. It will be used also here. Harry Blamires quotes some remarks from the critical work ob Thomas MacGreevy about Joyce in Our Exagmination Round His Factification for Incamination of Work in Progress, known as Exag, including James Joyce, himself and here it goes:

For Ulysses is an inferno. As Homer sent his Ulysses wandering through the inferno of Greek Mythology and Virgil his Aeneas through one of Roman Mythology so Dante himself voyaged through the inferno of the mediaeval Christian imagination and so Mr. Joyce sent his hero through the inferno of modern subjectivity.

It is very important to note that Blamires think this medieval three tips structuring was not quite achieved by Joyce and the only similarity is structural, as it has already been said.

But that's where the 3 chapters and 18 parts division comes from , with the names extracted from the Ulysses of Homer. Which is what we're using here:

Part	Homer's Ulysses adopted episode	Page number as at vintage Edition 1961 (brackets [n])
I -Telemachiade	Episode 1 - Telemachus	01 - 23
	Episode 2 - Nestor	24 - 36
	Episode 3 - Proteus	37 - 51
II - Odisseia	Episode 4 - Calypso	54 - 70
	Episode 5 - Lotus Eaters	71 - 86
	Episode 6 - Hades	87 - 115
	Episode 7- Aeolus	116 - 150
	Episode 8 Laestrygonians	151 - 183
	Episode 9 - Cila and Caribdis	184 - 218
	Episode 10 - Wandering Rocks	219 - 255
	Episode 11 - Sirens	256 - 291
	Episode 12 - Ciclops	292 - 345
	Episode 13 - Nausicaa	346 - 382
	Episode 14 - Oxen of the Sun	383 - 428
	Episode 15 - Circe	429 - 609
III - Nostros	Episode 16 -Eumaeus	612 - 665
	Episode 17 - Itaca	666 - 737
	Episode 18 - Penelope	738 - 782