Contents-Part 1.- General Introduction.- From the Bohr-Sommerfeld Theory to Quantum Mechanics.- The Goettingen Matrix Mechanics and Its Extensions.- Status of Quantum Mechanics in Early 1926.- Schroedinger's Work in Physics Prior to 1926.- Schroedinger's Personality and Method of Work.- Schroedinger and Wave Mechanics.- of this Volume.- I Schroedinger in Vienna (1887-1920).- 1.1 The Viennese Background.- An Apercu of Austrian and Viennese History.- The Viennese Culture.- Austrian Science up to the Middle of the Nineteenth Century.- The Foundation of Physics in Vienna.- Pioneers in Medicine and Psychoanalysis, Biology and Physiology.- Physiology, Physics and Cognition: Ernst Mach.- A Giant in Theoretical Physics: Ludwig Boltzmann.- Do Atoms Really Exist: Boltzmann or Mach?.- 1.2 The Young Erwin Schroedinger, His Youth and Study at the University of Vienna.- Schrodinger's Family and School Education.- Student at the University of Vienna.- Franz Exner and His School.- Fritz Hasenoehrl and Theoretical Physics.- Felix Ehrenhaft and Other Viennese Experimentalists: The Search for Subelectrons.- Two Pioneers of Radioactivity: Stefan Meyer and Egon von Schweidler.- The Institut fur Radiumforschung in Vienna.- Relativity and Quantum Theory in Vienna.- Schroedinger as a Graduate Student.- 1.3 The Early Scientific Work of Erwin Schroedinger.- Assistant at the II. Physikalisches Institut.- Schrodinger's Paper on the Kinetic Theory of Magnetism.- Ambitious Speculations on the Kinetics of Dielectric Substances and on the Theory of Solids.- The Review Article on Dielectrics and a Paper on Anomalous Dispersion.- Research on Atmospheric Electricity in Vienna.- The Penetrating Radiation and a Paper of Schroedinger.- The Hasenoehrl School.- Schroedinger and the Atomic Structure of Solids.- Lattice Dynamics and a Proof of the Atomic Structure of Solids.- 1.4 From Brilliant Pre-War to Dark War Days.- The Discovery of Cosmic Radiation (Hoehenstrahlung).- The 85th Versammlung Deutscher Naturforscher und AErzte.- Einstein's Talk at Vienna and Its Consequences.- Schroedinger as Privatdozent.- World War I and the Physicists.- Artillery Officer Erwin Schroedinger.- Heavy Losses.- The Later War Years.- 1.5 Schroedinger's Scientific Work in World War I.- An Analysis of Smoluchowski's Work on Fluctuations.- On the Evaluation of Statistical Data.- The Ultimate Proof of Schweidler's Fluctations.- Schroedinger and Quantum Statistical Theory in Vienna.- Problems and Ideas Connected with General Relativity.- Physics and Philosophy.- Atomic and Quantum Theory.- II Waves and Quanta: Preludes to Wave Mechanics.- II.1 The Dual Nature of Light.- The Origin of the Classical Concepts of Particles and Waves.- X- and ?-Rays.- Bragg's Corpuscular-Pair Theory of ?-Rays.- Heat Radiation and Its Description (1777-1900).- The Hypothesis of Light-Quanta (1905-1909).- Proof of the Light-Quantum (1916-1922).- II.2 The Side-Stages of the Development in Quantum Theory.- Early Centres of Quantum Theory: Berlin, Berne, Copenhagen, Munich.- Post-World War Centres and the Sommerfeld School.- Side-Stages: Breslau and Vienna.- Adolf Smekal and Quantum Theory in Vienna (1919-1923).- The Physikalische Berichte and the Encyklopadie Article; Start of Otto Halpern.- Paris and Modern Physics from 1900.- Quantum Theory in Post-War Paris: Dauvillier, L. Brillouin and L. de Broglie.- II.3 A Newcomer to Zurich: Erwin Schroedinger.- The Zurich Background: History of the City, University and E.T.H..- Mathematics and Physics at the E.T.H. (1855-1900).- Einstein, Debye and von Laue at the University of Zurich (1909-1914).- Physics in Zurich until 1920: Greinacher, Meyer, Bar, Ratnowsky, Wolfke.- Environment after World War I: Weyl, Debye, Scherrer, Schroedinger.- Development of Colour Theory from Newton to Schroedinger.- Colour Metric.- Causality and Chance: The Nature of Physical Laws.- II.4 Atomic Structure and Physiological Optics: General Research.- Programme of Schroedinger in Zurich (1922-1925).- Getting into the Theory of Atomic Structure.- Schroedinger's First 'Student': Erwin Fues.- A Letter from Fritz London Concerning an Extension of Weyl's Theory.- A Notable Property of Quantum Orbits.- Light-Quantum, Doppler Effect and Compton Effect.- Statistical Energy and Momentum Conservation.- Scientific Exchange with Sommerfeld.- Work on Colour Vision.- Last Papers on Colour Theory.- II.5 Problems and Extensions of Statistical Mechanics.- Isotopes and Gibbs' Paradox.- Extension of the Theory of the Specific Heats of Solids.- Thermal Equilibrium Between Light and Acoustic Rays.- Outlines of a Book on 'Molecular Statistics' and Related Unpublished Notes.- Handbook Article on Specific Heats and a Scattered Publication.- Specific Heat of the Hydrogen Molecule.- The Problem of Gas Degeneracy.- Planck's Problematic Division by N!.- Towards a New Statistics?.