  We study closed string evolution in the pp-wave spacetime assuming different
pulse shapes (square and sech-squared) in the exact gravitational wave metric.
It is shown that the shape of a circular closed string changes permanently to
an elliptical form after the pulse has departed. The worldsheet geometry also
displays characteristic permanent changes caused by the gravitational wave
pulse. The above effects collectively demonstrate features akin to what is
known as `memory' in gravitational wave physics.
