Pomona College, Clareniont, California 69 



Masterman's paper of 1898 is a very important one. He men- 

 tions Wagner, '47, as the first to describe the nervous system. Mas- 

 terman describes a central ventricular ganglion in the mid-dorsal 

 line at the base of the prae-oral lobe, composed of ganglion cells 

 and fibers. The ganglion is a proliferation of the inner cells of the 

 epiblast. Nerve tracts radiate in almost every direction. 



The nervous system may be summarized as follows : 



1. Central ganglion in front collar region and between this 

 and the prae-oral lobe. The epiblast in front is depressed to form a 

 neuropore. 



2. A ring about the posterior part of the collar is continued 

 dorsally and ventrally giving olT fine double groups of nerve tracts 

 to the anal end of the body. 



3. Groups of fine nerve tracts continued dorsally along the 

 trunk from the anterior end of the collar. 



Fig. 22. A. Section through body and central nervous system of Plioronis. 

 B. Small portion of lopophore showing depression. C. Small por- 

 tion of the nervous system of Phoronis enlarged to show nerve cells. 



