There are 6 lines in each of the stanzas.
Explanation:
The poem follows an unusual rhyme scheme so it is harder to pin down as it also constitutes close rhymes as rhymes but you can see that the poem actually has 6 line stanzas. This is evident if you notice the fact that:
the rhyme scheme in the first stanza follows something like this:
line 1 has a rhyme with the 4th line in still it and fill it
line 2 rhymes with line 5th with in it and linnet
line 3 rhymes with line 6th with go and slow.
This pattern makes the rhyme scheme to be abcabc and the pattern repeats itself in the next stanza. So the verses have 6 lines in a stanza.
