General Instruction of the Roman Missal: Chapter IV, The Different Forms of Celebrating Mass
C. The Duties of the Acolyte
187The duties that the acolyte may carry out are of various kinds and several may coincide. Hence, it is desirable that these duties be suitably distributed among several acolytes. If, however, only one acolyte is present, he should perform the more important duties while the rest are to be distributed among several ministers.
188In the procession to the altar, the acolyte may carry the cross, walking between two ministers with lighted candles. Upon reaching the altar, the acolyte places the cross upright near the altar so that it may serve as the altar cross; otherwise, he puts it in a worthy place. Then he takes his place in the sanctuary.
189Through the entire celebration, the acolyte is to approach the priest or the deacon, whenever necessary, in order to present the book to them and to assist them in any other way required. Thus it is appropriate, insofar as possible, that the acolyte occupy a place from which he can conveniently carry out his ministry either at the chair or at the altar.
190If no deacon is present, after the Prayer of the Faithful is concluded and while the priest remains at the chair, the acolyte places the corporal, the purificator, the chalice, the pall, and the Missal on the altar. Then, if necessary, the acolyte assists the priest in receiving the gifts of the people and, if appropriate, brings the bread and wine to the altar and hands them to the priest. If incense is used, the acolyte presents the thurible to the priest and assists him while he incenses the gifts, the cross, and the altar. Then the acolyte incenses the priest and the people.
191A duly instituted acolyte, as an extraordinary minister, may, if necessary, assist the priest in giving Communion to the people.[100] If Communion is given under both kinds, when no deacon is present, the acolyte administers the chalice to the communicants or holds the chalice if Communion is given by intinction.
192Likewise, when the distribution of Communion is completed, a duly instituted acolyte helps the priest or deacon to purify and arrange the sacred vessels. When no deacon is present, a duly instituted acolyte carries the sacred vessels to the credence table and there purifies, wipes, and arranges them in the usual way.
193After the celebration of Mass, the acolyte and other ministers return in procession to the sacristy, together with the deacon and the priest in the same way and order in which they entered.
D. The Duties of the Lector
Introductory Rites
194In coming to the altar, when no deacon is present, the lector, wearing approved attire, may carry the Book of the Gospels, which is to be slightly elevated. In that case, the lector walks in front of the priest but otherwise along with the other ministers.
195Upon reaching the altar, the lector makes a profound bow with the others. If he is carrying the Book of the Gospels, he approaches the altar and places the Book of the Gospels upon it. Then the lector takes his own place in the sanctuary with the other ministers.
196The lector reads from the ambo the readings that precede the Gospel. If there is no psalmist, the lector may also proclaim the responsorial Psalm after the first reading.
197When no deacon is present, the lector, after the introduction by the priest, may announce from the ambo the intentions of the Prayer of the Faithful.
198If there is no singing at the Entrance or at Communion and the antiphons in the Missal are not recited by the faithful, the lector may read them at the appropriate time (cf. nos. 48, 87).