THE NATURE AND STRUCTURE OF ACTIVE GALACTIC NUCLEI .2.

Our current understanding of the nature and structure of active galact ic nuclei is described, chiefly on the basis on optical spectroscopy, but including results of many authors, covering the entire observable wavelength of energy range. The importance of dust within the AGNs is emphasized, and current ideas of its distribution and of its effect on the observed spectra, are discussed. The torus model, polarization, a nd the ''hidden Seyfert 1'' nature of NGC 1068 and at least some other Seyfert 2 galaxies are discussed. It is likely that most QSOs, Seyfer t galaxies and LINERs form one family, and there may be many as yet un detected low-luminosity AGNs in apparently normal galaxies. A working hypothesis, involving refueling of inactive galactic nuclei through ga laxy interactions, is sketched.