Harris Hawthorne Wilder 449 



Details of Fixger Patterns in Duplicate Twins. 



It is with much hesitation that I venture upon a field so minutely 

 worked out in every detail by Mr. Galton, the more so as he has already 

 included among his labors a comparison of the patterns of three fingers 

 in the case of seventeen sets of twins/ by a coincidence the same number 

 presented here; since, however, he has in this made no distinction be- 

 tween duplicate and fraternal sets, it may not be superfluous to make 

 a short comparison of the formulas above given, and to present f ac-simile 

 prints of an actual case of true duplicates. 



My material is in a way incomplete, since I have rolled impressions 

 of but nine of the sets studied (N"os. I, III, VII, YIII, IX, X, XIII, 

 XIV and XV), and for the other cases have to rely upon the dabbed im- 

 pressions obtained, accidentally, as it were, while taking the general 

 palmar surface. As the fingers are somewhat flattened during this 

 process, the patterns are in most cases sufficiently complete for compari- 

 son except in the case of the thumbs of which the edges only appear, 

 save in those few cases in which the operators have had the forethought 

 to make a separate impression of each thumb. Where the pattern of a 

 thumb or other finger is in doubt I have placed a question-mark in the 

 formula. As shown by a cursory examination of the above formula3, the 

 results in the case of finger patterns are not very definite, and not only 

 is there frequently a lack of correspondence among the duplicates, but 

 there are also cases of undoubted fraternal twins in which the similarity 

 is remarkable. Thus, of the nine duplicate sets, not counting a reversal 

 of indices as a difference, Xos. II, III, V, XI, and XII (boys) correspond 

 completely, while Xos. I, IX, XIV and XV show differences (other than 

 reversals), in I the right thumb, in IX the right middle finger, in XIV 

 both sets of indices, and in XV the left index. In all the above the 

 numbers italicized show a reversal of an index pattern. Turning 

 now to the seven fraternal sets, Xo. VII shows four differences, IV and 

 XVI three each, VII, X and XVII, two each, and in XIII alone the 

 two formulae correspond — the doubtful case. As to the digits in which 

 the differences are located, in one instance it is the thumb, in ten the 

 index, in three the middle finger, and in two the ring finger. 



The above results may be more clearly expressed in the form of a table. 



Placed in this tabular form the records show at once the much greater 

 correspondence in the duplicate than in the fraternal set, since out of 

 nine sets of the former there are but six differences (aside from re- 

 versals), or 6f per cent, while in the seven sets of the latter there are 



' Finger-Prints, 1892, pp. 185-187, with Table XXVII. 



