ANCESTRAL CELLS IN 2-DIMENSIONAL SOAP FROTH

From the evolution of the ancestral cells in two-dimensional soap frot h, we find that the ancestral cell mean area [A(an)] decreases and the mean number of edges [n(an)] increases nonlinearly backwards in time. Unlike surviving cells, there is no sign of fixed point for the ances tral cells in our experiment. Also, the normalized mean area [A(an)(t) ]/[A(an)(t(f))] and mean number of edges [n(an)(t)] form scaling funct ions independent of t(f) >t with the normalized mean area [A(t)]/[A(t( f))] of the whole froth. These results agree with a dynamical simulati on for two-dimensional soap froths.