  We show that a product subsystem of a time ordered system (that is, a product
system of time ordered Fock modules), though type I, need not be isomorphic to
a time ordered product system. In that way, we answer an open problem in the
classification of CP-semigroups by product systems. We define spatial strongly
continuous CP-semigroups on a unital C*-algebra and characterize them as those
that have a Christensen-Evans generator.
