The Bar of stars and the Spiral Arms in Galaxy Evolution.

The Bar of stars and the Spiral Arms may be part of the same structure that spans the whole galaxy. If that spiral is unwound, to line up with the Bar, this will form a continuous double jet like structure from the Central Object to the Dark Halo. There will be no difference between the end of the Bar and the beginning of the Arms suggesting one harmonious process.
That process may be associated with the connection between galaxy evolution and the Central Object as the Bar, in this scenario, is formed by matter blasting off it's surface. A connection that is not possible of a Super Massive Black Hole but may be possible of a theorised White Hole.
The Spiral Arms are the Bar of yesteryear in a recognition of outward drift and rotation, from the Central Object, that forges the entire galaxy. Any merger would result in the deformation of the spiral which conflicts with the Standard Model.