Ivi 



INTRODUCTION. 



is au error. This ctecal appendage (see page xxv) is a 

 permanent feature of the alimentary canal in the species 



Fig. xii. 



Cell 0/Hypophorelln, with "Brown Body." 

 B. Brown body. pi. Plexus. FC. Fusiform cells, w. Wall of zocecium. 



in which it occurs, and has no special relation to the 

 development of the " brown body." I now agree with 

 Joliet in regarding it as due to a thickening of the outer 

 wall of the stomach, and not, as I once supposed, to a real 

 constriction of the part, indicating a gradual separation 

 of the lowest portion of the caecum from the rest of 

 the digestive canal. The question remains, whether the 

 "brown body" is formed out of the whole of the polypide 

 or merely out of the digestive sac. Joliet regards it as the 

 debris of the whole structure ; and his observations and 

 figures seem very conclusive so far as the species which he 

 examined are concerned. Smitt, if I understand him 

 rightly, holds that it originates from the stomach of the 

 polypide; and such M r as certainly* my own impression. 



