Note here that the  (= 1 + 2) in Figure (a) indeed reaches a minimum in a steady state, in agreement with Prigogine's theorem described previously, whereas the  in ex , which were 2, 3, 4, 5, 6, 7, and 810 -3 M in Figure (a), were simply changed to 4, 3, 2, 3, 4, 2, and 410 -3 M or 5, 4, 5, 3, 5, 4, and 510 -3 M, respectively, the other conditions being kept unchanged. Thus, the observation of the result in Figure (a), which is in agreement with Prigogine's theorem is regarded as happened by chance. These results thus indicate that Prigogine's theorem cannot be used for judging the stability of a steady state of an ORN against fluctuation. A plausible reason for such a conclusion is that many of reactions in ORNs are in the nonlinear region and besides most of reactions are not placed under a constant thermodynamic force and thus the reactions in ORNs do not meet the necessary conditions for Prigogine's theorem. It may also be pointed out that the number of reactions in an ORN often increases with the progress of reactions.