AVICULARIA. 



187 



astonishing rapidity, so as to form a cloud of living atoms around 

 the decaying body, quite visible in the aggregate to the unassisted 

 eye. An animal thus seized, therefore, becomes a centre to a 

 crowd of Infusoria, multitudes of which must be constantly drawn 

 into the tentacular vortex and swallowed by the Polyzoon. 





I' 1C. 187. PH'MATELLA. 



FlG. 



186. CELLULARIA AVICULARIA : a, natural size : b and c. portions much magnified, showing 

 the " birds' heads;" d, a single Polyzoon in its cell. 



Besides the marine genera above described, there are many 

 forms of animals, belonging to this class, that abound in our 

 fresh waters. These Fluviatile Polyzoa are to be met with in 

 ponds and streams, adherent to any foreign bodies that may be 

 casually submerged. Thus, they are found attached to stones at 

 the bottom of the water, upon shells, upon leaves more espe- 



