  Quadratic harnesses are typically non-homogeneous Markov processes with
time-dependent state space. Using an appropriately defined affine
transformation we show that all bridges of a given quadratic harness can be
transformed into other standard quadratic harnesses. Conversely, each such
bridge is an affine transformation of a standard quadratic harness. We describe
quadratic harnesses that correspond to bridges of some Levy processes. We
determine all quadratic harnesses that may arise from stitching together a pair
of q-Meixner processes.
