A tentative classification of galaxies with active nuclei

Proposes a bidimensional classification for galaxies with active nuclei (N galaxies, Seyfert galaxies, quasars and BL Lac objects) based on morphological and spectroscopic criteria. It is suggested that a quasar or an N galaxy should be called a Seyfert 1 if their spectrum shows broad Balmer lines; that an extragalactic star-like object should be called a quasar, even if it has the spectrum of a BL Lac object, etc. (36 refs).