158 



THE BIOLOGY OF TWINS 



demonstrate monozygotic origin, but lack of identity 

 does not disprove the possibility of monozygotic origin. 

 Wilder has illustrated certain very good cases of identity 

 by means of photographs of palm- and sole-prints (see 

 Fig. 52). The heavy lines are the lines of interpretation 



Fig. 53. — Photograph (from Wilder) of the left (above) and right 

 (below) palm-prints of a set of triplets. Note the close identity of the 

 males, which are evidently "identicals," and the unlikeness of these 

 to the female triplet on the right, which has evidently come from a 

 separate egg. 



and serve merely to emphasize a real, fundamental 

 identity. Another very interesting case is that of triplets 

 (two boys and one girl, Fig. 53) and illustrates very well 

 the difference between ordinary ''fraternal" resemblance 

 and true identity. The palm-prints of the girl are no 

 more like those of the two boys than is usually the case 



