1. From the Unit on Neurogenetics (L.R.C.) and the Section on Human Biochemical Genetics {LB., W.A.G.), Human Genetics Branch, National Institute of Child Health and Human Development, National Institutes of Health, and the Molecular Disease Branch (D.R., J.M.H.), National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Md. Address reprint requests to Dr. Gahl at the Human Genetics Branch, NICHD, NIH, Bldg. 10, Rm. 9S242, 9000 Rockville Pike, Bethesda, MD 20892.