Galaxies show a vast range of forms, and faced with any such
situation we would like to seek any underlying patterns. This
allows a compact description of individual objects, and if we
are fortunate will lead to physical understanding (the prototype
system of this kind is the MK stellar classification). Galaxy
classification has developed with this aim, from rough
description of an image through distinctions among components
with different astrophysical properties. It is important to keep
in mind that existing schemes are based on the appearance of a
galaxy at optical wavelengths (usually in blue light), over the
range of surface brightness conveniently recordable from the
Earth's surface. As such, these classifications are dominated by
certain components of galaxies. There are crude hand-waving
arguments implying that any outer faint structure might not be
fundamental dynamically - based on lack of star formation there
and the small number of crossing times at such distances - but
we certainly need to check,