APODA. 503 



BONELLIA, Rolando. 



Here the body is oval and furnished with a proboscis formed of a double 

 lamina susceptible of great elongation and forked at the extremity. The 

 intestine is very long 1 and frequently flexed, and we observe two ramified 

 organs which may serve for respiration. The ova are contained in an ob- 

 long sac opening" near the base of the proboscis. The Bonellije live at a 

 considerable depth in sand, extending- their proboscis to the water and even 

 to the air above its surface when the tide is low. 



B. viridis, Rol. It inhabits the Mediterranean. 



There are some other genera. 



CLASS II. 



ENTOZOA, Rud. 



The Entozoa or Intestinal Worms are remarkable, because the 

 greater number inhabit the interior of other animals, and there only 

 can live. There is scarcely a single animal that is not the domicil 

 of several kinds, and those which are observed in one species are 

 rarely found in many others. They not only inhabit the alimentary 

 canal and the ducts that empty into it, such as the hepatic vessels, 

 but even the cellular tissue, and the parenchyma of the most com- 

 pletely invested viscera, such as the liver and brain. 



In the Intestinal Worms we find neither tracheae, nor any other 

 organ of respiration, and they must receive the influence of oxygen 

 through the medium of the animal they inhabit. They present no 

 trace of a true circulation, and we merely perceive vestiges of nerves 

 so extremely obscure, that many naturalists have doubted their ex- 

 istence. 



When those characters are found united in an animal with a form 

 similar to that of this class, we place it here, although it may not in- 

 habit the interior of another species. 



We will divide the Entozoa in two orders, which are perhaps 

 sufficiently different in organization to form two classes, if we had 

 the observations requisite to determine their limits. These orders 

 are the Entozoa Nematoidea, Rud,, which have an intestinal canal 



