phenomenon of the dual leadership of the Babylonian academies which, with some slight interruptions, became a permanent institution and a weighty factor in the development of Babylonian Judaism. When Odaenathus destroyed Nehardea in 259—twelve years after Rav's death, and five years after that of Samuel—its place was taken by a neighboring town, Pumbedita, where Judah bar Ezekiel, a pupil of both Rav and Samuel, founded a new school. During the life of its founder, and still more under his successors, this school acquired a reputation for intellectual keenness and discrimination, which often degenerated into mere hair-splitting. Pumbedita became the other focus of the intellectual life of Babylonian Israel, and retained that position until the end of the gaonic period. Nehardea once more came into prominence under Amemar, a contemporary of Rav Ashi. The luster of Sura (also known by the name of its neighboring town, Mata Meḥasya) was enhanced by Rav's pupil and successor, Rav Huna, under whom the attendance at the academy reached unusual numbers. When Huna died, in 297, Judah ben Ezekiel, principal of the Pumbedita Academy, was recognized also by the sages of Sura as their head. On the death of Judah, two years later, Sura became the only center of learning, with Rav Chisda (died 309) as its head. Chisda had in Huna's lifetime rebuilt Rav's ruined academy in Sura, while Huna's college was in the vicinity of Mata Meḥasya (Sherira). On Chisda's death Sura lost its importance for a long time. In Pumbedita, Rabbah bar Nahmani (died 331), Joseph (died 333), and Abaye (died 339) taught in succession. They were followed by Raba, who transplanted the college to his native town, Mahuza (al-Mada'in). Under these masters the study of the Law attained a notable development, to which certain Judean-Palestinian scholars, driven from their own homes by the persecutions of Roman tyranny, contributed no inconsiderable share. After Raba's death, in 352, Pumbedita regained its former position. The head of the academy was Rav Nachman bar Yitzchak (died 356), a pupil of Raba. In his method of teaching may be discerned the first traces of an attempt to edit the enormous mass of material that ultimately formed the Babylonian Talmud. Not Pumbedita, however, but Sura, was destined to be the birthplace of this work. After Raba's death, Papa of Naresh, another of his pupils, founded a college in Naresh, near Sura, which, for the time being, interfered