Starting where Yeats and Owen left off, Dylan Thomas developed a system of consonantal correspondences which moved rhyme from the matching of same to the matching of similar sounds. His early verse abounded in such devices as zero consonance (rhyming, in a context of consonance, all syllables ending in an open vowel), partial consonance (rhyming two consonant clusters one of which is deficient in one or two members), close consonance (rhyming consonants which are phonetically similar rather than identical), and frame rhyme (rhyming words marked by both alliteration and consonance). In “Then was my neophyte” Thomas built an elaborate stanza by systematically associating and contrasting rhyming syllables according to the degrees of likeness among them. During the later thirties, however, he began to exercise increasing restraint in his use of the more unconventional of these consonantal devices; and although an unprecedented system of rhymes, founded upon assonance, began to take shape throughout the forties, it never quite attained the hierarchical articulation of the earlier consonant-based system. Instead, Thomas' latest work (his unfinished “Elegy”, for example) shows him preoccupied, just before his untimely death, with the exploration of simple, even quite traditional, stanzas based almost entirely upon conventional true rhyme.