Squares show spheroidals and plus signs show dwarf spiral and irregular galaxies.
The small dots are for globular clusters. Click on the plot for a larger version. This suggests that they are three distinct families of ellipsoidal stellar systems with different formation processes. The dSphs, previously thought to be the faint end of the sequence of ellipticals, are physically unrelated to ellipticals. The above results were derived using observed properties of the central parts of galaxies.