Rhymed Stanzas, Iambic Pentameter
Donne himself referred to this poem as a sonnet, which is con-PHEW-using since sonnets are those 14-line critters with a turning point and a rhyming couplet wrap-up. And this definitely doesn't fit that mode. Basically, Donne used "sonnet" to mean "any poem that deals with women and how much I love them."
This morrow serves up 21 lines, split into three stanzas of seven lines each. Most of the lines have 10 syllables, but each stanza peaces out with one 12-syllaber—just for kicks, giggles, and a little rhythmic variety. That means that 19 lines check in with iambic pentameter (five pairs of iambs, or an unstressed syllable that's followed by a stressed syllable) and 3 lines spread it out in iambic hexameter (six pairs of the same deal). Take a look:
And now good-morrow to our waking souls (8) 5 iambic pairs
Let us possess one world, each hath one, and is one (14) 6 iambic pairs
Donne also spices things up with a unique rhyme scheme that splits each stanza into a quatrain (a set of four lines rhyming ABAB), followed by a triplet (a set of three lines rhyming CCC). Each letter stands for the end rhyme sound for that particular line (so line 1 would have the same end rhyme as line 3). Look at stanza three to see how it pans out:
[…] appears (15) A
[…] rest B
[…] hemispheres A
[…] west B
[…] equally C
[…] I C
[…] die (20) C
Since rhymes tie lines together, this setup means that whatever's inside the quatrain hangs together. Same thing goes for the triplet. And you'll notice that Donne exploits this by making the quatrains more expository (that is, they tend to describe or explain things) and the triplets more interpretive. The speaker describes something in the first four lines and then uses the last three to reflect on it and draw bigger conclusions. In stanza two, for example, the quatrain explains how erotic love decreases their hunger to go a-traveling. The triplet responds to this fact with a series of rhetorical recommendations:
Let sea-discoverers to new worlds have gone,
Let maps to other, worlds on worlds have shown,
Let us possess one world, each hath one, and is one. (12-14)
In that way, then, each stanza is a mini-version of the poem as a whole: a description (of the couple's love), followed by a reflection (a celebration of just how groovy that love truly is). Nice work, Mr. Donne.