Harris Ha^\i;ho^ne Wilder 439 



or M-ith one or two slight differences due to the disposal of one or two 

 ridges at some critical point; and that, furthermore, these nine sets 

 are also " identical " in personal appearance. Of the remaining eight, 

 all of which differ as much in the palm and finger formulge as do 

 brothers and sisters of distinct birth, five of them, viz., Nos. IV, VIII, 

 XVI, XVII, and the girl of Xo. XII as compared with the boys, are 

 quite unlike in personal appearance ; two of them, Xos. VII and X, are 

 very similar but not identical, leaving Xo. XIII alone to present the 

 irreconcilable data of identical personal appearance with very different 

 formula. This set certainly damages the case to a slight extent, but 

 it is but one out of seventeen, or between 5 and 6 per cent, the remaining 

 sixteen being remarkably consistent in their relations to the main theory 

 of the paper. This theory would demand the disposal of Xo. XIII as 

 a case of fraternal twins in which the two members happen to resemble 

 one another closely, and as such cases may occur in separate births, it is 

 in no way remarkable that in those bom at the same time and subjected 

 as far as possible to the same environment after birth a chance resem- 

 blance might occur as great as in this instance. The placental condi- 

 tion at birth, employed at the beginning of this paper as an important 

 criterion, would very likely settle the question, but this it is impossible 

 to obtain. As a matter of coincidence it may also be possible to find a 

 case of unlike fraternal twins with very similar palmar formulae, thus 

 emphasizing the necessity of the identity of both formula and good physi- 

 cal characteristics as necessary concomitants in diagnosing" a case of 

 genuine identity. 



In tabular form the sets studied above may be classified as follows : 

 True duplicates, with correspondence of physical characters 

 and palmar formulae, Xos. I, II, III, V, IX, XI, XII (the 



two boys), XIV, XV. ^9 g^ts 



Fraternal twins, decidedly unlike both in personal appearance 

 and in palmar formulae, Xos. IV, VIII, XII (the girl in 

 comparison with the two boys), XVI, XVII (this last of 



different sex) ^5 gg^g 



Fraternal twins, that look much alike but with different palmar 



formulae, Xos. VII and X — 2 sets 



Twins, probably fraternal, with different palmar formulge, but 



strikingly similar in physical characteristics, Xo. XIII . . := 1 set 

 Of these the fraternal twins, being in no sense different from children 

 of separate birth, will interest us no further in the present discussion, but 

 the nine sets of duplicates deserve a careful consideration and may now be 

 taken up in detail. 



