The ΔY/ΔZ abundance ratio is studied taking into account mass loss from intermediate and massive stars, and the Yz vs. Z relation of Peimbert and Serrano (1980a).

Since I am here, I have been asking myself why on earth have I been chosen by the Organizing Committee to this final and quite uneasy job to formulate some concluding remarks to the enormous complexity of this conference. And the only reason I can find, is that I am the least competent person to do so among all the people gathered in this room, as I have never directly put my hands, nor very deeply speculated, on any of the items which have been here discussed. I feel however somewhat encouraged by the belief that the secret wisdom which has dictated my choice was precisely to select an outsider whose function should essentially consist to look at things from a certain distance, with no a priori opinions related to so many unsettled questions. And therefore I shall mostly try to keep myself in such a role asking in advance for forgiveness for all the shortcomings to which my lack of specific differentiated knowledge may have induced me to commit.