1. Development and Aetiology -- Development -- Aetiology -- 2. Morphology -- Classification Systems -- Structural Organization of Holospheric Brains. Coauthor: A. Brun -- Associated Malformations -- The Pseudo-Callosum -- Gross Morphology of Typical Specimens -- 3. Neuroradiology -- General Notes and Conventional Radiology -- Pneumoencephalography -- Positional Anomalies of Primitive Holospheres -- Angiography -- Case Reports -- 4. Review and a New Classification System -- Critical Review and Comments on the Current Classification System -- A New Classification System -- 5. Differential Diagnosis -- Partial and Complete Callosal Defects with Interhemispheric -- Defects of the Septum Pellucidum -- Hydranencephaly -- References