From the Institute of Obstetrics and Gynaecology, Queen Charlotte's Hospital, London.

Submitted for publication Jan. 23, 1961.

We would like to thank the consultant staff at Queen Charlotte's Hospital for access to case records of patients under their care, Dr. A. E. Claireaux for his detailed autopsies of the central nervous system malformations, and Prof. J. H. M. Pinkerton for his help in the preparation of this paper.