The Morphology of Cosniobia 371 



Part 1. The "Baldwin Synote/' a human monster of the im- 

 PERFET Janus type. 



A. General consideration of the Janus-Omphalopagus Series. This is 

 an extensive natural series of Cosmobia, certain of the stages of which 

 are among the most frequent of mammalian symmetrical monsters. In 

 this series the two components are placed vis-a-vis, that is, with the ven- 

 tral sides applied to each other, and with always a common umbilicus. 

 Individuals of this series may vary in two ways, not dependent upon 

 each other; (1) in the extent of longitudinal union, and (2) in the 

 amount of lateral torsion of the two components in respect to each other. 

 These will be considered in order. 



1. Variations in the extent of longitudinal union. The posterior 

 limit of this union is always fixed by the umbilicus, to which it extends 

 in all cases and beyond which it never goes, leaving, posterior to this 

 point, in undeformed Cosmobia, two perfect hinder parts, facing each 

 other. Even in cases with extreme involution of one side (as described 

 under (2)) this peculiarity becomes less and less posteriorly, and by the 

 time the umbilical level is reached the components exactly face each other. 



The stages in such a series are shown in the accompanying diagram. 

 (Fig. 2.) Each stage figured rests upon actual cases, and typical ex- 

 amples are indicated by the name of the authority and the date of the 

 descriptive paper, so that the cases can be easily found by refernce to a 

 teratological bibliography. As the diagram represents merely the extent 

 of union longitudinally, each case is represented with the components 

 exactly opposite, that is, with no lateral torsion. The series thus begins 

 with a "Janus symmetros," in which the line of union begins at the 

 vertex and extends, as in all the cases, to the innbilicus. In the second 

 stage the brows, eyes, and noses become free, although the latter may be 

 hindered from full development through lack of room. In the third 

 stage the face is free as far as the chin, and in the fourth the heads 

 and necks are free and the union begins at the manubrium sterni. In 

 the stage following the union begins at the mesosternum, but in the next 

 it involves the xiphisternum alone. The extreme type of this series is 

 one in which the entire sternum is free and the soft parts alone are 

 involved. Such were the famous "Siamese twins," Chang and Eng. 



Beyond this there is introduced a stage in which the united parts 

 include only extra-embrj^onal structures, as, for instance, a portion of 

 the umbilical cord or even the placenta alone. Such a case would be a 

 true Cosmobion, but as the united structures are cast away at birth 



