It is only several decades since galaxies were recognized as huge aggregations of matter in the universe which consist of myriads of stars and vast clouds of gas. The wide variety of shapes of galaxies is one of the wonders of the universe. Attempts to classify galaxies have continued since an early stage of study, when they were still called nebulae.
The first step towards classification was a grouping of the patterns; the second step a systematic arrangement of various morphological types. Classification schemes that are in present use, such as Hubble's, are in the second group. These...