de Vaucouleurs Revised System

1) The 3-D system. Principal axis is stage, vertical axis is bar, and the in-out axis is ring. The overall shape indicates the maximum variety occurs in the middle of the spiral sequence. (click to enlarge)

2) The 3-D system redrawn in 2-D by folding out, with Ellipticals at the center and irregulars on the outside. Up-down is Barless-Bar; left-right is noring-ring.

3) Cut through the 3-D system near Sb; sketches to illustrate the features.

4) Ditto, with example galaxies inserted.