Studies of the yields of muonium atoms and diamagnetic-species in hexane in the presence of added scavengers have shown, unequivocally, that muonium is not formed by the "delayed" (microsecond) mechanism proposed recently. Instead, the lifetimes evaluated show that if the combination reaction of mu(+)+e(-)-->Mu contributes to muonium formation in "chemically active" liquids, then it is complete within <10(-10) s. In fact the results are consistent only with the "hot" model, in which the initial distribution of muons between muonium atoms and diamagnetic molecules is determined at the epithermal level, as the last step of the muon's charge-exchangecycles and thermalization. (C) 2003 American Institute of Physics.