The results are reported of testing 1073 English bloods with the Rh antibodies anti-C, anti-Cw, anti-c, anti-D, anti-E and anti-e. The results of another series of 927 bloods, already published, are here reproduced. The total of 2000 bloods has been used by Fisher to estimate, by his method of maximum likelihood, the Rh chromosome frequencies in England. The estimates are: CDe 40.75 per cent, cde 38.86 per cent, cDE 14.11 per cent, cDe 2.57 percent, CwDe 1.29 per cent, cdE 1.19 per cent, Cde 0.98 per cent, and CDE 0.24 per cent.

A brief account is given of the three pairs of alternative antigens shown by Fisher to be the basis of the Rh blood groups. Fisher’s interpretation must now be considered as established beyond doubt. A possible genetic basis of these related antigens is discussed.

ACKNOWLEDGMENTS We are deeply indebted to Professor Fisher for many reasons, but we should particularly like to acknowledge his kindness in allowing us to publish the results of his calculations of the chromosome frequencies. For the antisera used in the investigations we are indebted to the following: Doctors E. F. Aubert, Sheila Callender, D. S. Dick, R. J. Drummond, Mr. I. Dunsford, Doctors A. J. McCall, Brenda Morrison, J. Murray, E. Wordley and R. A. Zeitlin. We also thank Dr. H. F. Brewer of the London Red Cross Blood Donor Service, and Dr. J. F. Loutit of the National Transfusion Service, for providing us with large numbers of blood samples. We also wish to acknowledge the assistance of Dr. Marjory N. McFarlane in the earlier part of this investigation.