VARIATION AND HEREDITY IN TWINS 163 



ments either at birth or in later Hfe as data for determin- 

 ing the degree of resemblance (coefficient of correlation) 

 between twins. 



Modes of inheritance of friction-ridge patterns. — 

 In his recent studies on the palms and soles of human 

 beings, Wilder has brought out some very interesting 

 and significant facts about the inheritance of certain 

 of these patterns. Without going into the details of 

 classification or codification of patterns, it may be said 

 that palm and sole configurations are markedly herit- 

 able. A comparison of the prints of the right palm 

 of a certain father and his six-year-old son"^ show how 

 exactly these details may be duplicated in two successive 

 generations. Certain elements in the palm pattern, 

 for instance, seem to be inherited after the manner of 

 Mendelian unit characters, strongly marked patterns 

 of unusual types being dominant over less marked ones. 



An interesting possible development from these 

 facts has to do with the use of these patterns in deter- 

 mining the parentage where there is doubt about the 

 matter. If a certain unusual type of pattern were 

 found in either supposed parent and the same pattern 

 appeared in the supposed offspring, the relationship 

 might be said to be established with a high degree of 

 probabiHty. If, on the other hand, such a pattern 

 failed to appear or appeared only in a highly modified 

 form, the conclusion of lack of relationship would not 

 be safe; there is always the chance that a combination 

 pattern, derived by a mixing of the patterns of the two 

 parents, might occur, or even that a grandparental 

 pattern, recessive for one generation, might reappear. 



^ See Wilder, loc. cit. 



