174 THE BIOLOGY OF TWINS 



and there are marked differences in height and weight. It will be 

 noted that in these there is a complete lack of the bilateral 

 symmetry in the hands of one individual, which is usual, though 

 not invariably the case, in undoubted duplicates. Were the 

 theory established beyond a doubt, I should unhesitatingly 

 diagnose this as a case of fraternals in whom there happens to be 

 striking resemblance, but as one cannot be dogmatic, I must 

 leave it as recorded, without explanation. The finger prints 

 correspond exactly in the two individuals, even more than is 

 usual in those twins that are unquestionably duplicates, yet it 

 will be noted that they are, in the main, ulnar loops, the common- 

 est type of pattern. 



This, in my opinion, is unquestionably a case of 

 duplicates and exhibits conditions quite parallel to 

 those shovv^n by armadillo quadruplets. 



These rather long but significant quotations serve to 

 show the difficulty of applying, as a criterion of mono- 

 zygotic origin of twins, resemblances or lack of resem- 

 blances in any unit characters. It would seem, on the 

 whole, more feasible to trust to one's judgment of the 

 general similarity in features, coloring, disposition, and 

 the like, for such resemblances are at least as important 

 elements in the personality as are finger-prints; a 

 general summation of resemblances is more likely to 

 be a sound basis than any single detail could be, espe- 

 cially since we know that monozygotic armadillo 

 quadruplets often differ markedly among themselves 

 in respect to characters of strictly comparable nature. 

 The presence of any type of symmetry reversal would 

 to my mind outweigh any lack of detailed resemblance 

 in deciding that any given set of twins is monozygotic. 



Whether in the light of these circumstances Wilder's 

 idea is justifiable — that we can measure the limits of 



