136 



ANIMAL BIOLOGY 



The anemones are mostly sessile animals attached at 

 the base or foot to rocks or seaweed. They are common 

 on rocky parts of the coast and some forms may be exposed 

 at low tide. Many species are remarkable for their 



beauty of form and coloring. 

 The free end, or disk, is fur- 

 nished with tentacles which are 

 employed in catching prey and 

 conveying it to the mouth. 

 Anemones are more highly 

 organized than the hydroids. 

 The digestive cavity is divided 

 by a number of partitions, the 

 mesenteries, which extend from 

 the body wall toward the cen- 

 ter. In some species the edges 

 of these mesenteries bear long 

 extensile filaments, armed with 

 nematocysts, which are capable 

 of being thrust out of the body 

 when the animal is irritated. 



Closely related to the ane- 

 mones are the corals. In a 

 typical coral the body of the 

 individual animal, or polyp, has 

 the property of secreting about 

 its base, a hard deposit of car- 

 bonate of lime, forming the so- 

 called coral rock. As coral 

 polyps commonly multiply by budding they may form an 

 extensive society of individuals more or less closely asso- 

 ciated with one another. The masses of coral rock which 

 the polyps form may be increased almost indefinitely 

 by the multiplication of the polyps and the accession 



FIG. 112. Portugese man-of- 

 war. (After Agassiz.) 



