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GEORGE WAGNER. 



monstrosity consisting of two complete embryos united at the 

 breast bone. For some reason or other one gains a start in 

 development. As their circulatory systems are united (as is 

 believed, and in many cases demonstrated) this stronger indi- 

 vidual (autosite) soon drives its blood into the other (parasite), 



FIG. 3. (After Adami, after Wintersohn.) 



the heart of which then degenerates through disuse. This 

 means a less adequate blood supply, atrophy, and a lesser or 

 greater absorption by the stronger individual. It is easy to 

 see that the later in the embryonic period the inequality begins 

 the more extensive in development will the parasite be. 



I have not attempted to seek all the cases of this sort in man. 

 Approximate parallels of that shown in Fig. 3 must be, to judge 

 from the literature, quite rare. As to the lower vertebrates I 

 have not been able to find a record of any case closely similar 

 to this. It is an interesting fact to note that a frog could grow 



