26 



ON CLASSIFICATION. 



but is bent upon itself (Fig. 8), and the direction of flexure is 

 such that the nervous ganglion, which corresponds with those 

 called "pedal" in Lamellibvanchiata, is placed in the re-entering 

 angle between the gullet and the rectum. In order to express 



Fig. 8. 



Fig. 8. — Phimatella repens, a single cell more magnified ; m, calyx at the base of the 

 ciliated tentacula borne by the disk or lophophore ; k, gullet; g g, stomach; /<, in- 

 testine; i, anu> ; w, nervous ganglion (after Allman). 



this relation of the nervous system to the alimentary canal, the 

 flexure of the latter has been called " neural " — the side of the 

 body on which the principal ganglion is placed, and towards 

 which the intestine is bent, being the " neural " side. AYhatever 

 our terminology, however, the great point is to remember that 

 the structural relation which it expresses is constant throughout 

 the Polyzoa. 



In the next division, the Bkachiopoda, which are animals 

 differing very much in external appearance from the Polyzoa, 



