It has been shown in an earlier paper (Lorber, 1965) dealing with the family history of 722 infants born with spina bifida cystica or encephalocele, that 6 8% of 1256 sibs were also affected, either by the same condition or by the closely allied lesions of anencephaly or congenital hydrocephalus. This high incidence in sibs is suggestive of hereditary factors playing a part in the causation of ...