D O C . 1 5 3 P R E S E N T I N G PA P E R S T O A C A D E M Y 1 6 9 3. Mr. Einstein presented a paper by Prof. Dr. Erwin Schrödinger in Zurich on “The Energy Levels of the Ideal Monatomic Gas Model.” (Appears later.)[3] Mr. Planck has based a quantum theory of ideal gas on the assumption that the totality of N! elementary states, assumed by permutation of the molecules, should be treated as a single elementary state aside from this principle, he also introduced a kind of quantization of the states of the individual molecule. The author bases his theory only on the first-mentioned assumption by Planck, hence he does not intro- duce any quantization rule for the individual molecules quantum states of the gas correspond to cells in phase space of the volume N!h3N.