82 HEREDITY AND EUGENICS 



normal length. Although brach3'dactylous individuals 

 are lacking in some forms of dexterity, and therefore 

 must accept a lower social status, yet they show a 

 decided increase in fecundity compared with normal 

 members of the same family. In this family twenty- 

 five now living in England and Wales are brach}^- 

 dactylous. Beginning with the fourth generation, the 

 total number of descendants from DR x RR* crosses 

 is seventy-five, of whom thirty-nine are abnormal. 



No connection could be traced between Drink- 

 water's first brachydactylous family and the one 

 described by Farabee, there being no surname common 

 to the two families. Drinkwater (191 5) has since 

 described another family, how^ever, which he has 

 shown to be descended from a member of Farabee 's 

 familv, who removed from America and settled in this 

 country. In this family and its American ante- 

 cedents the abnormality can be traced for six genera- 

 tions. In both branches of this family the proportion 

 of females among the abnormals is exactly 61 per cent. 

 In the English branch fifty abnormals were recorded 

 to forty-eight normals, where 50 per cent, of each 

 type were expected, showing that heterozygous 

 brachydactyls produce the two types of germ cells in 

 equal numbers. Normals mated together invariably 

 have only normal offspring. The shortness of stature 

 of brach3^dactyls is shown to be due to the short legs, 

 both femur and tibia being shorter than in normal 

 members of the family. 



Drinkw^ater has also described in two families the 

 condition which he calls minor brachydactyly (191 2, 

 1 91 4). In a Lancashire famil}^ this abnormality has 

 been traced through five generations, and sixteen 

 abnormals were living when the study was made. 

 The fingers are less shortened than in brachydactyly, 



* D=dominant, R=recessive, hence DR is a heterozygous 

 dominant. 



