In this first attempt at constructing an atlas of this sort, we have arranged the systems following the lead of Arp (1966). In particular, we define several broad morphological classes, but make no clear breaks between the classes, and the objects are often arranged so that the last objects of one class are similar to the first objects of the following one. Overall, the major motivation for placing an object on a specific page is to have it appear between systems that it most resembles.
These classes are defined morphologically, and within each category, objects are presented in a suggestive sequence. The order within a class is sometimes motivated by dynamical considerations, e.g., the arrangement of interacting galaxies in a suggested evolutionary sequence. These motivations and guiding principles are explained in the following sub-section, which also gives detailed motivations for placing some specific objects in one sequence rather than another.
Table 1 shows the arrangement of the Gallery, along with the criteria for ordering of objects within classes, and Table 2 lists the individual galaxies in the order in which they appear. As mentioned above the last object of one class is often similar to the first object of the next one. The classification of galaxies is a very subjective task, and many systems could easily fit into several categories. This is a work in progress and we welcome your comments.