The term "amaurotic family idiocy" comprises a large group of disorders in which there are more or less definite pathologic changes. Here belong the infantile type of Tay1-Sachs,2the late infantile variety described by Jansky,3Schob,4but especially well studied by Bielschowsky5and the juvenile form of Vogt6and Spielmeyer.7Ichikawa8accepts six varieties in which, he states, the changes, especially the retinal, as well as the clinical features are practically alike. Vogt, Spielmeyer and Bielschowsky also class with amaurotic family idiocy cases of exquisitely hereditary and familial cerebral disorders recorded by Pelizaeus,9Higier,10Merzbacher11and one lately reported by Wolpert.12However, like many other cases of blind idiocy, such as Winkler's,13these have little in common, either clinically or anatomically, with the three well studied types mentioned above. Possessing common clinical features—blindness and progressive mental