Semi-major axis a versus time t (bottom panel), and the embryo mass M_em versus t (top panel) for the simulation with 120 low-mass 0.1M_⊕ embryos. Colours correspond to the embryo number to distinguish the individual orbits. The final state is depicted as a series of filled circles, with sizes proportional to the masses. The evolution is never regular but rather chaotic, partly due to direct N-body gravitational interactions among the embryos, but more importantly due to overlapping spiral arms(see also Fig. 18). Initially, there are only several mergers that create a handful of 0.2M_⊕ embryos. These grow preferentially by the pebble accretion; there are a few additional mergers.