THE UEADSHAW LECTURE 21 



female, or it may be caused by a tendency to the 

 division of a fertilised ovum, which tendency may 

 be transmitted either by the male or female 

 parent. ' Mr. Rooth, in describing his case of 

 Brighton united twins, gives the following family 

 history : 



The grandmother of the children had four separate births 

 of twins as well as other children, and was herself a twin. 

 The mother of these children was one of these twins.* 



That is, he records four generations of twins on 

 the female side. 



The following case, as indicating the influence 

 of the male parent, I give on the authority of 

 Dr. Wormell, formerly headmaster of the Cowper 

 Street Schools : An intimate friend and neighbour 

 married, and his wife on two occasions gave birth 

 to twins. After the second birth the wife died. 

 Subsequently the gentleman married again, and 

 his second wife gave birth to twins. ]n all these 

 cases each pair of twins was of the same sex. 



Among domesticated animals twins are encour- 

 aged in sheep, because the greater the number of 

 lambs the greater the profit as mutton, so ewes 

 which throw habitually only one lamb are weeded 

 out of a flock. On the other hand, among cows 

 the profit is from the milk, and a cow that gives 



* 'Brit. Med. Journ.,' September 23rd, 1911, p. 654. 



