The first printed Othello is the first Quarto (Q1), 1622; the second is the first Folio (F1), 1623.  These two texts are two distinct versions of the play.  Q1 contains many oaths and expletives where less ‘objectionable’ expressions occur in F1.  Partly for this reason it is believed to represent the earlier text, perhaps the text as it stood before the Act of 1605 against profanity on the stage.  Its readings are frequently superior to those of F1, but it wants many lines that appear in F1, which probably represents the acting version in 1623.  I give a list of the longer passages absent from Q1: 

     (a) I. i. 122-138.  ‘If’t’ ... ‘yourself:’ 

     (b) I. ii 72-77.  ‘Judge’ ... ‘thee’

     (c) I. iii. 24-30.  ‘For’ ... ‘profitless.’

     (d) III. iii. 383-390. ‘Oth. By’ ... ‘satisfied! Iago.’

     (e) III. iii. 453-460.  ‘Iago.’ ... ‘heaven,’

     (f) IV. i. 38-44.  ‘To confess’ ... ‘devil!’

     (g) IV. ii. 73-76, ‘Committed!’ ... ‘committed!’

     (h) IV. ii. 151-164.  ‘Here’ ... ‘make me.’

     (i) IV. iii. 31-53.  ‘I have’ ... ‘not next’
                and 55-57. ‘Des. [Singing]’ ... ‘men.’

     (j) IV. iii. 60-63.  ‘I have’ ... ‘question.’

     (k) IV. iii. 87-104.  ‘But I’ ... ‘us so.’

     (l) V. ii. 151-154.  ‘O mistress’ ...  ‘Iago.’

     (m) V. ii. 185-193.  ‘My mistress’ ... ‘villany!’

     (n) V. ii. 266-272.  ‘Be not’ ... ‘wench!’

Were these passages after-thoughts, composed after the version represented by Q1 was written?  Or were they in the version represented by Q1, and only omitted in printing, whether accidentally or because they were also omitted in the theatre?  Or were some of them after-thoughts, and others in the original version?

I will take them in order. (a) can hardly be an after-thought.  Up to that point Roderigo had hardly said anything, for Iago had always interposed; and it is very unlikely that Roderigo would now deliver but four lines, and speak at once of ‘she’ instead of ‘your daughter.’  Probably this ‘omission’ represents a ‘cut’ in stage performance. (b) This may also be the case here.  In our texts the omission of the passage would make nonsense, but in Q1 the ‘cut’ (if a cut) has been mended, awkwardly enough, by the substitution of ‘Such’ for ‘For’ in line 78.  In any case, the lines cannot be an addition. (c) cannot be an after-thought, for the sentence is unfinished without it; and that it was not meant to be interrupted is clear, because in Q1 line 31 begins ‘And,’ not ‘Nay’; the Duke might say ‘Nay’ if he were cutting the previous speaker short, but not ‘And.’ (d) is surely no addition.  If the lines are cut out, not only is the metre spoilt, but the