the Office of the saint. d) In the Office of Readings, the biblical reading with its responsory is that assigned to the weekday. The hagiographical second reading with its responsory is proper to the saint, but if no proper reading is assigned, the reading is either taken from the Common or is the patristic reading of the weekday e) Prayer during the Day and Compline are taken entirely from the weekday. Celebrations of memorials occurring between 17 and 24 December and during Lent, which are then never obligatory, consist of adding to the Office of Readings, after the patristic reading and responsory of the weekday, the hagiographical reading and responsory of the saint, and concluding with the prayer of the saint; and adding to Lauds and Vespers, after the concluding prayer of the weekday, the antiphon (proper or common) and the prayer of the saint. Obligatory and optional memorials Memorials are either obligatory or optional. The rules governing the celebration of memorials, whether obligatory or optional, are identical. The only difference is precisely that an optional memorial need not be observed, and, with the limitations indicated for the second part of Advent and for Lent, there is the possibility of celebrating instead the Mass either of another memorial assigned to that day, or of the weekday, or of any saint mentioned in the Roman Martyrology for that day, or indeed (except during the first part of Advent, the days from 2 January to the day before Epiphany, and Eastertide), a Mass for Various Needs, or a Votive Mass. Sometimes memorials that are called obligatory cease to be such. This occurs to those that fall within Lent. If two obligatory memorials coincide (as can happen when the movable memorial of the Immaculate Heart of Mary falls on the date of a fixed obligatory memorial), both become optional. Pre-Vatican II forms of the Roman Rite In approximate correspondence to memorials, Pope John XXIII's 1960 Code of Rubrics spoke of "third-class feasts, as can be seen in the General Roman Calendar of 1960, and gave some of them, either permanently or on the occasions when their celebration coincided with one of higher rank, only a commemoration within the office actually celebrated. The Code of Rubrics laid down that, unless proper psalms are assigned, a third-class office uses the weekday psalms and at matins combines the second and third readings for the ferial day