Ponicina Ccille^c, Clait-ninnt. Cnlifciinia 



67 



spicuous cord in contact with the epithelium and projecting slightly 

 into the basement membrane. The center is of a clear substance 

 and about this center are nerve cells. 



Harmer, 1917, in Phoronis oralis gives the position of the 

 nerve ring which he shows thickened on the dorsal side. 



I have had some opportunity to study P. pacifica and a species 

 of Phoronapsis. It is quite important in studying the serial sec- 

 tions of this group that rather perfect preparations be available, a 

 condition not altogether easy, as sand often interferes with gootl 

 sections. However a number of perfect preparations were ob- 

 tained. 



In general I found the nervous system much as already indi- 

 cated by the many of the others. In P. pacifica I found central 

 nervous svstem to have its chief concentration a little below the 



Fig. 21. A. Section showing position of nervous system off /ioi Jin's- after 

 Schneider. B. Nervous system in Phoronis after Schneider. C. 

 Diagram of a reconstruction of the nervous system of Phoi-oiiif! show- 

 ing longitudinal nerve cord on the right. Not all of the nervous sys- 

 tem going to the tentacles is shown at the left. D. Section of nerve 

 cord with epithelial cells on the outer surface and basement mem- 

 brane in dark below. E. Actinotrocha larva showing the nervous 

 system after Inedia. F. Diplochorda, after Masterman. 



