  A special type of immigration associated with measure-valued branching
processes is formulated by using skew convolution semigroups. We give
characterization for a general inhomogeneous skew convolution semigroup in
terms of probability entrance laws. The related immigration process is
constructed by summing up measure-valued paths in the Kuznetsov process
determined by an entrance rule. The behavior of the Kuznetsov process is then
studied, which provides insights into trajectory structures of the immigration
process. Some well-known results on excessive measures are formulated in terms
of stationary immigration processes.
