176 HEREDITY IN RELATION TO EUGENICS 



Fig. 159. — A case of polydactylism. The boy's father has 12 fingers 

 and 12 toes, but the e.xtra fingers are boneless. Besides the boy figured, 

 who is like his father, there is 1 son with extra toes, 1 with extra toes and 

 an extra finger on the left hand only. One sister has extra toes only. The 

 other 5 children were normal in respect to the number of toes and fingers 

 they bear. Through the kindness of Professor C. A. Scott. 



from the trait, though of the polydactyl strain, will probably 

 have only normal children. 



g. Syndactylism. — ^The union of the bones and tissues 

 of two or more digits into one mass is found in many animals 

 including man. I have studied it in hundreds of fowl. It is 

 inherited there, as no doubt also in man, in such fashion as 

 to permit the conclusion that syndactylism is due to a factor 

 that extends the web paripassu with the development of the 

 digits. On this hypothesis the normal hand or foot lacks 

 the factor and two normal persons (even of a syndactyUc 



