170 



COELENTERATA. 



If the skeleton has the form of isolated needles or toothed rods 

 (Fig. 140) of calcareous substance deposited in the jelly of the 



coenenchyma (or polyp), the 

 polyp-stock has a fleshy, leathery 

 nature (Alcyonarid) ; but if, on 

 the contrary, the calcareous 

 structures are fused or cemented 

 together, a solid, more or less 

 firm, calcareous skeleton is de- 

 veloped (Corallium, Tubipora)'. 

 Finally, the skeleton may be of 

 a stony character and secreted 

 by the ectoderm of the lower 

 part of the polyp (Madre- 

 poraria). 



The important diversities of 

 form in the polyp-stocks are 

 not only occasioned by the 

 differences of structure of the 

 skeleton of the polyp, but are 

 also the resultant of varying 



Fio. 140. -Calcareous bodies (Sclerodermites) of methods of growth by gem- 

 AJcyonaria (after Kolliker). a, of Plexaurella ; ma ti ll and imperfect fission. 

 6, of Gorgonia ; c, of Alcyoniitm. 



According to the method, nu- 

 merous modifications of branched stocks are 

 distinguished, e.g., Madrepores (Fig. 141), Ocu- 

 linidae (Fig. 142), and the lamellar and massive 



stocks as Astraea (Fig. 



143) and the Maeandri- 



nidae (Fig. 144). 



The Antliozoa are all 



inhabitants of the sea, and 



live mostly in the warmer 



zones, but certain types of 



the fleshy Octactinia and 



Actinia are distributed in 



all latitudes. Some genera 



of the Madreporaria are 



FlG.Ul.-Madreporaverru- found ill the deep Sea, 



where they may form accu- 

 mulations of considerable extent, but the polyps which take the 



Ed. H.). 



