Top left panel: evolution of the surface abundances in mass fraction as a function of the actual mass of the star for the non-rotating 60   M_⊙ model. Different evolutionary phases are indicated in the upper part of the figure. A very narrow region, just before the WC phase, corresponds to the WNC phase (not labelled in the figure for clarity). Bottom left panel: evolution of abundance ratios (in number) as a function of the actual mass of the star. Right panels: Same as the left panels for the rotating model.