1882.] Structure, Development, and A jjinities of Phoronis. 383 



Two diagrams to illustrate the body plan of Phoronis, Brachiopoda, and Polyzoa. 



A. Longitudinal vertical section through the adult animal. 



B. Longitudinal horizontal section through the adult animal. 



E.p. Praeoral lobe or epistome. 

 m. Mouth. 

 a. Anus. 

 os. (Esophagus. 

 s.t. First stomach. 

 jp. Second stomach. 

 r. Intestine. 

 v.t. Right tentacle of ventral pair. 

 y.t. Eight tentacle of dorsal pair. 

 p.b.c. Body-cavity of head. 

 f.b.c. Body-cavity of foot. 

 N.r. Postoral nerve-ring. 

 v.m. Yentral mesentery. 

 l.m. Lateral mesentery. 



n. Nephridium. 

 E.o. External opening of nephridium. 

 i.o. Internal opening of nephridium. 

 p.d. Posterior chamber of body-cavity. 

 l.a.d. Lateral anterior divisions of body-cavity. 

 V.V. and D.Y. Valves of Brachiopod shell. 



A.B. Represents axis perpendicular to which ordinary segmentation takes place. 

 -C.D. Represents axis perpendicular to which Brachiopoda have been supposed to be 

 segmented. 



