24 From what We have written, Venerable Brothers and Beloved Sons, it follows that it is all-important to supply your different fields of labor with as many native priests as shall be sufficient, by their individual efforts, to extend the conquests of Christianity and to rule the faithful of each nation without the necessity of depending upon the help of a foreign clergy. In some places, as We have already pointed out, seminaries for the native clergy have been opened. These seminaries are being erected in points central to the nearby missions and entrusted, as a rule, to the same religious order or congregation which has charge of the missions. At these central institutions the Vicars and Prefects send their chosen men and pay for them while they are being trained, to receive them back one day ordained priests ready for the sacred ministry. This policy, which has been followed in some places, We sincerely wish, nay, We command, shall be followed likewise by the Superiors of all missions, so that it cannot be said that any native youth has ever been kept out of the priesthood and the apostolate, provided, of course, he exhibits the mark of a true vocation and is a young man of genuine promise.
Source: Rerum Ecclesiae (Vatican.va)