464 Duplicate Twins and Double Monsters 



fertilized ovum which controls the development down to considerable 

 detail. If the premises concerning the genesis of duplicate twins are 

 true, we have given us by nature the convincing experiment of the sepa- 

 rate development of two identical eggs, containing identical bits of germ- 

 plasm, derived from the same original male and female germ-nuclei. 



Indeed, we have for comparison the control experiment of the develop- 

 ment of two different eggs simultaneously in the same uterus and under 

 identical conditions, with results as different as might be expected from 

 the premises, showing that the correspondence in the one case and the 

 lack of it in the other are both based upon the composition of the germ- 

 nuclei and are in no way affected by subsequent conditions of develop- 

 ment. 



2. Concerning the correspondence of palm and sole patterns in the 

 various sorts of twins (and triplets) the present investigations have 

 yielded the following results : 



a. Out of ten sets in which the physical resemblance was sufficiently 

 remarkable for them to be considered duplicates, nine corresponded so 

 completely in the palm patterns that out of 104 points compared (main 

 lines, triradii and patterns) 94 were exact duplicates, and of the ten 

 differences, two were probably due to an incompleteness in the print, 

 while the remainder were very slight and usually due to an aberrancy in 

 a single ridge. The tenth set (No. XIII) did not correspond. 



b. In seven sets of twins that did not resemble one another (including 

 the girl trij)lets as compared with the boys), there was no more corre- 

 spondence between the palms of the two individuals than is usual in 

 members of the same family. 



c. The study of the sole prints of seven of the duplicate and two of 

 the fraternal sets (all that I have) yielded the same results as in the 

 case of the palms. 



d. The finger patterns of duplicate twins are very similar, but in 

 place of exact correspondences there sometimes occur patterns which 

 are easily derived from one another but which would have different 

 formula in Galton's system. The differences of this kind are especially 

 apt to happen in the index fingers; they sometimes occur also in the 

 thumbs, and have been noted once in middle fingers. 



e. In the case of duplicates the following additional phenomena have 

 been observed in the majority of cases, but are not universal : 



(1) A bilateral correspondence in the two palms or soles of each indi- 

 vidual of a set. 



(2) A reversal of the finger patterns in either the right or the left 

 indices. 



