NED Abstract 
Copyright by Astronomical Society of the Pacific.
Reproduced by permission

1958PASP...70..364M

    A Preliminary Classification of the Forms of Galaxies According
                      to their Stellar Population

                               Morgan, W.
               Yerkes Observatory, University of Chicago

                                ABSTRACT
   A revised system of classification of the forms of galaxies is
described. The principal criterion of type is the degree of central
concentration of the light of each galaxy; in this respect the new
system can be considered a modification to that of Hubble. 
   The basis for the new classification is the spectroscopic work on
composite spectra of galaxies by Morgan and Mayall. The correlation
between form and stellar population found by these investigators has
been utilized to set up a form classification which would be indicative
of the general kind of stellar population encountered in the majority of
galaxies classified.
   A total of 608 galaxies have been classified in the new system from
plates obtained principally by Edwin Hubble in the Mount Wilson-Palomar 
collection.
   Possible application of the new classification to problems of galactic
distribution and evolution are outlined. There is a definite indication
of large-scale fluctuations in the average stellar population
characteristics of galaxies within distances corresponding to redshifts 
of around 2000 km/sec.