SNIPPET: Legion of Mary, an association of lay Catholics, founded in 1921 by Frank DUFF (1889-1980). Its members' practical Christian action is rooted in a theologically based spirituality, inspired by the writings of St. Louis Marie Grignion de MONTFORD (1673-1716). Organizationally influenced by the Society of St. Vincent de Paul, it consists of a network of local conferences, called praesidia, under regional concilia. Members attend weekly meetings and engage in practical mission work. Because it was lay run and theologically sophisticated, it was suspect, for a time, by Dublin archbishops Edward BYRNE and John Charles McQUAID. The movement has been extraordinarily successful abroad, per Thomas O'CONNOR, Lecturer in Modern History, National University of Ireland, Maynooth, Kildare.