14 PROCEEDIlSrGS OF THE NATIONAL MUSEUM vol. 81 : art. 16 



peritoneal side after development to the sexually immature adult 

 has taken place in the liver. 



In the case of G. didelphis it seems likely that there is a similar 

 course of development, for the worms found, although large and 

 with all the features characteristic of adult gnathostomes, contained 

 no eggs. There was, however, no indication of a migration from the 

 liver to the stomach. It might be conjectured, by analogy with 

 G. spinigei'wn^ that this would shortly have occurred. It is also 

 possible, however, that the opossum is not the normal host, and that 

 the normal migration out of the liver after the last molt had for 

 that reason failed to occur. There can be little doubt that the oc- 

 currence of sexually immature gnathostomes in cysts in various parts 

 of the body of human beings is likewise due to failure of normal 

 migration in a foreign host, in this case resulting in misdirected 

 movements. 



