This poem, Noctiluca, by Anthony Loi of the Writing Program is a sestina, a famously
(or infamously) complicated verse form invented in the twelfth century by the wandering
singers  known as troubadours.  A sestina contains six six-line stanzas and a three-line
conclusion (or envoy).  The sestina eschews rhyme in favor of a fixed pattern of end words,
which must be repeated in a different (and specific) order in each stanza.  The envoy must
complete the end-word variations and also contain the remaining three end words. 
--David Thorburn, poetry editor