8 It is necessary that missionaries obey the words of Our immediate predecessor, Pius XII, to the effect that they "must constantly keep before their mind's eyes their ultimate goal, which is to establish the Church firmly in other countries, and subsequently to entrust it to a local hierarchy, chosen from their own people.'' (15) Therefore, this Apostolic See, abundantly and at the opportune time, has taken measures especially in recent times, to establish or re-establish a hierarchy in those areas in which local conditions favored the foundation of Episcopal Sees, and if possible, to place locally born prelates at their head. At any rate, it is well known that this has always been the principal and constant goal of the Sacred Congregation for the Propagation of the Faith. It was an Apostolic Letter, however, which highlighted the importance and immediacy of the matter as never before. In this letter Our predecessor, Benedict XV, urgently reminded the authorities in charge of the missions to nurture carefully the vocations of those who felt the divine call to the priesthood in mission territories and to contribute to the quantitative and qualitative growth of that clergy which was called native. (Neither slight nor discrimination was intended by the word "native," or was ever expressed or implied by the language of the Roman Pontiffs and ecclesiastical documents.)
Source: Princeps Pastorum (Vatican.va)