  Fragment production has been studied as a function of the source mass and
excitation energy in peripheral collisions of $^{35}$Cl+$^{197}$Au at 43
MeV/nucleon and $^{70}$Ge+$^{nat}$Ti at 35 MeV/nucleon. The results are
compared to the Au+Au data at 600 MeV/nucleon obtained by the ALADIN
collaboration. A mass scaling, by $A_{source} \sim$ 35 to 190, strongly
correlated to excitation energy per nucleon, is presented, suggesting a thermal
fragment production mechanism. Comparisons to a standard sequential decay model
and the lattice-gas model are made. Fragment emission from a hot, rotating
source is unable to reproduce the experimental source size scaling.
