This poem is written in dimeter, which means that there are two main beats per line. As for the individual lines, though, the poetic feet change in order to accommodate the number of syllables in Hughes' chosen words. A Poetic foot is a pattern of stressed and unstressed syllables, and there are many types of poetic feet. The most common is the iamb, which is a two-syllabic foot comprised of an unstressed followed by a stressed syllable (like the word "deferred"). The other two-syllabic foot is a trochee, which is made up of a stressed syllable followed by an unstressed syllable (such as the name "David"). Hughes uses iambs for his two-syllable feet in this particular poem. However, as part of his rhythm (which is syncopated... that's a musical term meaning that the rhythm is varied and comes unexpectedly, not in a repeated pattern), Hughes uses words and phrases that have more than two syllables, even though he maintains that there are only two STRESSED syllables in a line (that's where the DImeter comes from). In music, perfect four/four timing has only four beats per measure, and the quarter note gets each beat. It would be a boring song that is written stictly in quarter notes, so the song writer will use a vairety of notes to break the monotonous rhythm; however, in order to maintain the time signature (four/four), the song writer must make sure that the notes can fit into a measure mathematically. It's similar with poetry. If you think of the meter as the time signature, and the poetic feet as the variety of notes, you can see how Hughes' rhythm is created. Read the poem aloud, and while you do so, snap your fingers in a rhythmic beat. As you are reading, you will find that there are only two "snaps" per line, even though the number of syllable changes (that's where you use "two eighth notes" instead of one "quarter note" to put it in musical terms).