It would be highly unusual to see a worm now that places an artificial limit
on its own propagation, but that was exactly what the Xerox worm did. The
Xerox worm was composed of multiple segments, by way of analogy to real
biological worms; at most one worm segment could run on any one machine.
A bounded, finite number of segments were started, and all segments kept in
contact with one another. If the worm lost contact with a segment (for example,
someone rebooted the machine that the segment was running on), then the other
segments sought another machine upon which to run a segment.