250 COMPARATIVE ZOOLOGY. 



radiating canals, which ramify and open into a circular 

 vessel, and a " veil," or shelf, always running around the 

 mouth of the disk. 129 



CLASS II. Anthozoa. 



These marine animals, which by their gay tentacles con- 

 vert the bed of the ocean into a flower-garden, or by their 



secretions build up coral-islands, 

 have a body like a cylindrical 

 gelatinous bag. One end, the 

 base, is usually attached ; the 

 other has the month in the cen- 

 tre, surrounded by numerous 

 hollow tentacles, which are cov- 

 ered with nettling lasso -cells. 

 This upper edge is turned in so 

 as to form a sac within a sac, 



FIG. 198. Horizontal Section of Ac- 

 tinia through the stomach, show- like the neck of a bottle turned 



ing septa aud compartments. . . _ 



outsidem. The inner sac, which 



is the digestive cavity, does not reach the bottom, but 

 opens into the general body-cavity. 130 The space between 

 these two concentric 

 tubes is divided by a 

 series of vertical parti- 

 tions, some of which 

 extend from the body- 

 wall to the digestive 

 sac, but others fall 

 short of it. Instead, 

 therefore, of the radi- 

 ating tubes of the Aca- 

 leph, there are radiat- 

 ing spaces. No mem- 

 bers of this class are 



Fid. 199. Actinia expanded, seen from above, 

 microscopic. All are showing mouth. 



