Questions of attribution and chronology in 3 medieval texts on species theory

Three medieval treatises, the Prologus in tonarium by Bern of Reichenau, Ci ta et vera divisio monochrodi, and Duo semispheria, are linked by virtue of their species theory, in which the ecclesiastical modes are constructed us ing species of diatessaron and diapente. In 1978, Joseph Smits van Waesberg he investigated the complicated interrelationships between these texts and made certain determinations concerning the attribution and dating of two of them. This essay argues against Smits van Waesberghe's hypotheses by exami ning and comparing the texts of the three treatises.