250 



COMPAEATIVE ZOOLOGY. 



naria in its usually larger size and solid disk, four radiat- 

 ing canals, which ramify and open into a circular vessel, 

 running around the margin of the disk.™ 



Class II. — Anthozoa. 

 These marine animals, which by their gay tentacles con- 

 vert the bed of the ocean into a iiower-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 mouth, in the cen- 

 tre, surrounded by numerous 

 hollow tentacles, which are cov- 

 ered with nettling lasso -cells. 

 This upper edge is turned in so 

 ™ ,„c n ■ . , o .- . . as to form a sac within a sac, 



Fia.198.— Hiirizontiil Section of Ac- ' 



tinia throngh the stomach, show- like the Ueck of a bottle tumcd 

 lug septa and comnanments. • ■, • mi ■ i • i 



outside in. 1 he inner sac, which 

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

 into the general body-cavity (Fig. 38)."° 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 Aea- 

 leph, there are radiat- 

 ing spaces. No mem- 

 bers of this class are 



. , ,, Fia. 199. —Actinia expanded, seen from abovb 



microscopic. All are Bhcwiug month. 



