QSOs are believed to reside in the cores of massive galaxies or, perhaps at the highest redshifts, in dense condensations that later become the cores of massive galaxies. See, for example, Kormendy et al. (1998), Magorrian et al. (1998) for the black hole-host galaxy connection, McLure et al. (1998), McLeod (1998), Aretxaga et al. (1998), Bahcall et al. (1997), Miller et al. (1996), McLeod & Rieke (1995) for direct observations of QSO hosts, and Turner (1991), Haehnelt & Rees (1993), Loeb & Rasio (1994), Haehnelt et al. (1998), Haiman & Loeb (1998) for theoretical links between QSOs and galaxy formation.