in the color of the arc as a function of position along it, but only at a modest $\sim 0.3$ mag level of significance, larger than the color differences among A1, A2, B, and C (Table 2). If a lack of variation were confirmed, say, at the $\sim 0.03$ mag level, it would become a much stronger argument against patchy extinction in G, and in favor of extinction in the host galaxy of the QSO, rather than in G. Further high-resolution IR studies of the system will provide improved constraints on the location of the extinction. With B. McLeod, we intend to continue optical and IR studies both from the ground and with HST.

Because it appears aligned with the continuation of the arc past B, object X seems morphologically associated with . If it were not in the foreground of G (the least interesting possibility), we could have: (1) $z_{\rm X} \sim z_{\rm QSO}$, (2) $z_{\rm G} < z_{\rm X} < z_{\rm QSO}$, or (3) $z_{\rm X} \sim z_{\rm G}$. In the first case, X could be expected to have a counter-companion (a counter-arc in our example, or at least a second image likely to be at least as 