No. 4S5] 



THE DETERMINATION OF SEX 



307 



duced by counting such twins as two births. Of the eighteen 

 cases of twins and triplets considered by Wilder (:04), twelve 

 pairs of duplicate twins were females. If such a large propordon 

 of all duplicate twins should be females, the error introduced 

 would be considerable, and the preponderance of male births 

 increased. The number of cases given, however, is too small to 

 warrant drawing conclusions as to the relative frequency of male 

 and female duplicate twins. 



The sexual ratio. — The sexual ratios for eleven European 

 countries, as they existed sometime during the latter part of the 

 nineteenth century, have been taken from the tw enty-eighth annual 

 report of the Massachusetts State Board of Health through the 

 courtesy of the late Dr. Samuel W. Abbott. The figure for Eng- 

 land from 1628 to 1642 is that given by Lexis ('92). The ratio 

 for the United States was computed from 2,021,955 births — 

 1,038,432 males and 983,523 females — the statistics for which 

 were furnished by the health officers of the various states liaving 

 reliable statistics of births. 



German Empire (1 871-1 S80) 1062 



Switzerland 1063 



Austria 1067 



Italy 1071 



France 1063 



Belgium . . . . • 1058 



Holland 1063 



Denmark 1058 



England (modern times. Living births only) . 1038 



England (1628-1642) 1068 



Sweden 1060 



Norway 1061 



Massachusetts (1876-1896) sdll births included . 1066 



Massachusetts (1856-1875) living births only . . 1055 



United States 1056 



Mean of all ratios 1060 



