Eight lines of iambic pentameter with a rhyme scheme of ABABABCC? Sounds like ottava rima to Shmoop. But before you go hunting for your Italian dictionary, we'll give you the breakdown.
We've already covered the rhyme scheme in our "Detailed Summary," (check it out, in case you missed it), so here, we'll cover this whole iambic pentameter thing. Take a look at the first line:
I sought a theme and sought for it in vain
Feel the da-DUM rhythm? This line is composed of five da-DUMs, and each da-DUM is what we call an iamb, like "I sought." That's a type of metrical foot. When you have five of these feet in a row, we call it pentameter. So this line, and much of the rest of the poem, is in iambic pentameter, because that's the meter ottava rima requires.
Now here's the cool part: ottava rima was also traditionally an Italian poetic form. It was usually used in epic poems – poems that traced the successes of a hero through battles, saving damsels in distress, and all other sorts of fun.
Hmm…Shmoop smells some irony. "The Circus Animals' Desertion" is in the form of a traditional epic, but who ever heard of an epic featuring circus animals? Most wild, mythic battles don't come complete with caramel corn and a trip through the fun house mirrors.
Sure, Yeats goes through the motions of bringing up the heroes and heroines of old – in fact, Section II is pretty much a whirlwind tour through mythology and epic romance. But he's yanking all of these characters onto stage in order to point out all the ways that they're not useful anymore.
Using ottava rima in a poem that isn't an epic (at least in the traditional sense) can make readers feel like the rug has been pulled out from beneath them. That's actually just fine with Yeats. See, his speaker (er… the poet) has had the rug ripped out from under him, too. We might as well suffer along with him.