454 Duplicate Twins and Double Monsters 



the palmar configuration, a fact which may be due to the greater import- 

 ance of the individual ridges in the formation of the patterns, and to the 

 close morphological interrelation between the four primary types. It 

 may be definitely stated, however, in the case of duplicate twins (1) that 

 the finger patterns correspond far more completely than in those of the 

 fraternal type, (2) that the differences are more apt to appear in the 

 thumbs and indices, and (3) that these latter patterns show a strong 

 tendency in one hand or the other towards a reversal, i. e., the formation 

 in the two individuals of patterns which are the symmetrical equivalents 

 of one another. To these conclusions may be added (4) that twinned 

 digits in a single individual, at least in the case of double thumbs, do 

 not necessarily possess duplicate patterns. 



The Sole Configurations in Twins. 



As material for this study I have the sole prints of seven sets, five be- 

 ing .duplicates (I, II, III, XII, XV) and two fraternal (IV, VII). 

 As far as it is safe to draw conclusions from so small a number they 

 exhibit the same principles as those shoion hy the palms and are in some 

 ways rather better for study since they often possess a more complex 

 configuration. In general, it may be said that the soles of duplicates 

 exhibit the same striking correspondence in main lines and in patterns as 

 do the palms, as well as the same tendency to a bilateral symmetry when 

 the tivo sides are compared; also that in fraternal twins there is either 

 a striking contrast or else the similarity, at best, is no greater than among 

 other members of the same family. 



In detail the observations of the different sets are as follows : 



Duplicates. 



I. In these the four soles are all exact duplicates and belong to what may 

 be called the simple type, one in which the four main lines and all inter- 

 vening ridges cross the inner margin and form no loops or patterns during 

 their course. The only pattern present is the 1st interdigital or hallucal 

 (the "thenar" of previous articles) which is reduced to a simple loop open- 

 ing upward between the 1st and 2nd toes. There is no definite lower triradius 

 on any of the feet, but there are rudiments of one in all, situated between 

 lines B and C. 



II. In this set the right footprint of x is wanting owing to a slight injury 

 received just previous to the printing and rendering it unwise to attempt a 

 print. The comparison is thus confined to the two lefts, but as the remaining 

 right, that of y, is the symmetrical equivalent of the others, there is little 

 room to doubt that the missing foot would also be a duplicate of the other 

 three. The configuration of these soles is rather complicated and as it shows 

 with especial clearness the principle expressed in the case of the hands, that 



