THE UROGENITAL SYSTEM 611 



as well as beneath the peritoneal epithelium from which they seem to 

 arise. 



Just after metamorphosis, these cell-groups separate from the peri- 

 toneum to form the network mentioned. 



The medullary portion, however, has a totally different origin, and 

 one which may throw light on further work in our study of ductless 

 glands, whose secretions have become an important factor in modern 

 medicine. This portion is derived from the ganglia of the sympathetic 

 nervous system by groups of cells whose precise origin is not clear. 

 Some of these cell groups remain in the sympathetic ganglia, but others 

 migrate to the adrenal body and become scattered about. 



