180 HEREDITY IN RELATION TO EUGENICS 



41. Twins 



It is well known that twin production may be an hereditary- 

 quality. Thus the Dorset race of sheep is characterized by 

 the tendency to bear twins. In man, too, strains are known 

 where plural births are the rule. Remarkable cases are re- 



FiG. 165. — Of 2 twin sons one has a pair of twin sons and 5 single bom 

 children; the other had 1 son. The former has, through his sons, 3 pair of 

 grandchildren; the latter 1 pair. Waklet, 1895. 



corded by Stocks (1861, p. 78), see Fig. 164, and by Wakley 

 (1895, p. 1289). See Fig. 165. 



In the foregoing cases inheritance of the twinning capacity 

 is through the males only, and this is true in some strains of 

 sheep. However, other human strains are known with the 

 tendency to twin-production passing along the female line. 



