THE BIOLOGY OF TWINS 163 



and temperament, intonation and handwriting. 

 It may be both interesting and useful to recall some 

 of the extraordinary illustrations of the close re- 

 semblance of duplicate twins, developed, as the 

 armadillo story makes clear, from one egg. Mr. 

 Galton tells of a case in which no one, not even the 

 twins themselves, could distinguish their hand- 

 writing; of another case in which " a doubt re- 

 mains whether the children were not changed in 

 their bath, and the presumed A is not really B, 

 and vice versa"; of two girls who used regularly 

 to impose on their music teacher, one of them taking 

 two lessons in succession when the other wished 

 a whole holiday; of a schoolmaster who, to make 

 sure, used to flog both twin-brothers when one had 

 sinned ; of nine cases where a twin addressed his or 

 her reflection in a mirror in the belief that it was the 

 other twin in person; of four or five cases of doubt 

 during an engagement of marriage ; and of a quaint 

 interchangeableness of expression, " that often gave 

 to each the effect of being more like his brother 

 than himself." The depth of the constitutional 

 sameness is said to be sometimes seen in the twins 

 sharing some special ailment at the same time or 

 showing the same exceptional peculiarity. " Two 

 twins," Galton noted, " at the age of twenty-three 

 were attacked by toothache, and the same tooth 

 had to be extracted in each case." Two closely 

 similar twin-brothers, of similar tastes and pro- 

 fession, died of Bright's disease within seven months 

 of each other. Sometimes the resemblance is 



