Hubble subdivided these three classes into finer groups according to subtle differences in shape, as described in detail below. Other classification schemes similar to Hubble's follow this pattern but subdivide the galaxies differently. A notable example of one such system is that of Gerard de Vaucouleurs. This scheme, which has evolved considerably since its inception in 1959, includes a large number of codes for indicating different kinds of morphological characteristics visible in the images of galaxies. The major Hubble galaxy classes form the framework of de Vaucouleurs's scheme, and its subdivision includes different families, varieties, and stages, as shown in Table 1.