I think the speech is in order, but I have been confused by the headings of each section. Sometimes they are single paragraphs, other times they are more.

The headings read as follows:

1I. When, O Catiline, do you...

2 Shame on the age...

3 What? Did not that most illustrious...

4II. The senate once passed a decree...

III. For what is there, O Catiline, that you can still expect...

IV. Listen while I speak of the night before...

9 O ye immortal Gods, where on earth are we?

So this has been confusing for me. Neither the regular numerals nor the roman numerals seem to follow one another, and they don't seem to be subsets. My guess would be they're compiled from two sources; and only surviving parts of each source are outlined, which account for gaps in the numerals as well as overlap in them.

EDIT: also more details, without adding the whole text; in section III, in the same paragraph there exists regular numerals preceding sentences:

7Do you recollect that on the 21st of October...

8What? when you made sure that you would be able to seize Praesneste

So this seems to make the regular numerals follow, as 5 and 6 are found embedded in the preceding 4II section. This makes the regular numeral 9 that follows consistent with how these regular numerals progress. So really its two sections of numerals progressing, nothing seems to be lost here. What does each type of heading represent?

EDIT: the work with the headings can be found here