8 



" remain attached to the side of the o-lass a considerable 

 " time. They are very easily kept in confinement for 

 " years : but, as with many of their allies, great diminn- 

 " tion of bulk occurs, from deprivation of the natural 

 " supply of food. AVhen recently captured specimens are 

 " placed in a jar containing injured Annelida, numerous 

 " fa3cal masses, cjnsisting of the l)ristles of Xcirla jiclariica, 

 " and other annelids and digested matter, are found lying 

 " on the bottom of the vessel, sliowin"' how yieedilv tliev 

 " have fed : a fact, indeed, very easily ascertained by 

 "actual ol)servation. It is also frequently noticed that 

 " specimens confined in vessels along with the deep green 

 ''Kii/(i/i<( r/i-/(iis assume a similar hue, probably from 

 " feeding on the rejected debris of those animals, if not 

 " upon the latter themselves. In their native haunts the 

 " stones under which they lie are often placed on dark, 

 " muddy, and highly odoriferous *and or gravel, and the 

 " water cannot be otherwise than brackish at the estuary 

 " of a river."' 



BODY WALL AXD MUSCULAK SYSTEM. 



The outside of the animal is completely covered with 

 cilia, which are borne by long slender cells (PI. II., tig. ■!), 

 widest externally where they carry the cilia, antl narrow- 

 ing to a ver}' tine process which is somewhat liranched. 

 and is inserted into the basement membrane. They con- 

 tain small elongated nuclei in the more external portion. 

 The larger and more rounded nuclei found in the 

 epidermis are for the most part connected with the large 

 greenish unicellular gland cells occurring all over the 

 skin. These last stain vividly Avith picric acid or with 

 eosin, and it is probably their contents which give the 

 skin its markedly acid reaction. These two forms of ceil 

 constitute the main mass of the epithelium, though it is 



