DUPLICATE TWINS AXD DOUBLE MONSTEES. 



BT 



HARRIS HAWTHORNE WILDER, Pii. D. 



From the Zoological Lahoratory of Smith College. 

 With 2 Plates and 11 Figures in the Text. 



Having recently called attention to the great similarit}' in the config- 

 uration of the epidermic ridges on the palms and soles of identical 

 twins/ and seeing that the subject is one involving important biological 

 problems, it has seemed to me of importance to collect as much evidence 

 as possible on this head, and place it in convenient form, that it may 

 serve as a basis for future speculation. 



Furthermore, as identical or duplicate twins have not been generally 

 defined save by the somewhat untrustworthy criterion of facial resem- 

 blance, and as their close relationship to certain of the types included 

 under the head of double monsters has not been clearly emphasized, I have 

 begun the paper with a discussion of the general subject. This portion 

 of the paper, which presents a series of the most important data con- 

 cerning twins and compound monsters, will serve as a necessar}^ back- 

 ground for the facts presented in Part II, which constitutes the more 

 original part of the investigation. Part III presents the deductions as 

 far as they seem indicated, but is intended more as an aid in directing 

 speculation in the future than as a set of dogmatic assertions which 

 would be at present premature. 



Part I. 



MULTIPLE BIRTHS AND THEIR RELATIONSHIP TO COMPOSITE 



MONSTERS. 



Duplicate and Fraternal Twins. — It is well known that there are, 

 at least in the human species, two types of twins ; the first include those 

 cases where the sex may or may not be the same and where the general 

 resemblance is about what ma}^ be expected in the case of any two children 



^ Cf. Palms and Soles, in Amer. Jour. Atiat., Vol. I, p. 42.3, Nov., 1902. 

 American Journal of Anatomy. — Vol. III. 



