19 Before everything else, We call your attention to the importance of building up a native clergy. If you do not work with all your might to attain this purpose, We assert that not only will your apostolate be crippled, but it will become an obstacle and an impediment to the establishment and organization of the Church in those countries. We gladly recognize and acknowledge the fact that in some places steps have already been taken to provide for these needs by the erection of seminaries in which native youths of promise are well educated and prepared to receive the dignity of the priesthood, and are trained to instruct in the Christian Faith members of their own race. But in spite of all this work, we are still a great distance from the goal which we have set for ourselves.
Source: Rerum Ecclesiae (Vatican.va)