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Published online by Cambridge University Press: 14 August 2015
It is generally assumed that quasi-stellar objects represent phenomena taking place in galaxies. There are at least three lines of reasoning that lead to this viewpoint. First, there appears to be a continuity of properties extending from Seyfert galaxies and N systems to QSOs with the differences between the various groups principally a question of the contrast between the luminous central object and its surrounding galaxy. Since Seyfert galaxies and N systems are definitely in galaxies, it is concluded that QSOs must also be in galaxies which are not directly visible because of the high luminosity of the central object. A second argument is based on the result that QSOs do not appear to differ dramatically in abundances of elements from those which are typical of normal galaxies. With the prevailing view that virtually all the elements heavier than helium originated as a result of stellar processes, it would be concluded that QSOs must be associated with galaxies of stars that produced the heavier elements. A third, rather indirect argument is based on the results of Stockton (see his paper in this volume) and others that QSOs are often found in groups of galaxies and therefore are likely to be located in galaxies themselves (guilt by association). But the fact is that direct evidence that QSOs are in galaxies is sadly lacking.