WORMS. 199 



bladder, supporting one short head, provided with four 

 suckers. About as large as a pea. they are found in the 

 cellular or membranous portions of hogs, and render tho 

 flesh unfit to be eaten. 



THIRD ORDER. 

 ZOOPHYTES OR R A D I A T A . 



This division of the animal kingdom comprehends two 

 principal classes, namely Polypi andi Sea Stars (asteria). 

 The former have larger or smaller sized bodies, with an 

 opening on one of the extremities, surrounded by radii 

 or long tentacles, and live either singly or in companies. 

 In the first case they are soft and without any encasing 

 tegument ; in the second they form a common dwelling 

 composed of calcareous matter ; this solid envelope as- 

 sumes various forms, and constitutes small cells or tubes, 

 each of which contains a polyp ; the aggregated mass is 

 called coral. The sea-stars, on the other hand, always 

 live singly ; the body is in the form of a star with five 

 rays ; the outer covering is either coricaceous or calcare- 

 ous. 



The Armed Green Polypus (hydra viridis) has a 

 transparent cylindrical body, resembling a gelatinous 

 tube, with from six to twelve tentaculae on the free ex- 

 tremity. In length one inch, and about as thick as the 

 tube of a crow quill; the filaments surrounding the 

 mouth longer than the body, which they can extend or 

 shorten at pleasure. These polyps live in fresh water 

 ponds everywhere in Europe. Their presence is easily 



