Ivi 



INTKODUCTION. 



is an error. This csecal appendage (see page xxv) is a 

 permanent feature of the alimentary canal in the species 



Fig. xxi. 



\UM--:^^-J^ 



Cell o/Hypophorella, with " Brown Body." 

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



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

 development of the " brown hodj." I now agree Avith 

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

 wall of the stomachy 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 was certainly my own imj)ression. 



