  A metamorphic robotic system (MRS) consists of anonymous modules, each of
which autonomously moves in the 2D square grid by sliding and rotation with
keeping connectivity among the modules. Existing literature considers
distributed coordination among modules so that they collectively form a single
MRS. In this paper, we consider distributed coordination for two MRSs. We first
present a rendezvous algorithm that makes the two MRSs gather so that each
module can observe all the other modules. Then, we present a merge algorithm
that makes the two MRSs assemble and establish connectivity after rendezvous is
finished. These two algorithms assume that each MRS consists of five modules,
that do not have a common coordinate system. Finally, we show that five modules
for each MRS is necessary to solve the rendezvous problem. To the best of our
knowledge, our result is the first result on distributed coordination of
multiple MRSs.
