CORALS. 



Anthozoa or Actinozoa. 



153 



ZOANTHARIA, HeXACORALLA, £.g^., 



Sea Anemone. 



Many are simple, many colonial. 



Tentacles usually simple, usually some 

 multiple of six, often dissimilar. 



Mesenteries usually some multiple of six, 

 complete and incomplete. 



Retractor muscles never as in Alcyonaria. 



Two gullet grooves or siphonoglyphes, or 



only one. 

 Dimorphism only in some Aniipatharia, 



and in one Madrepore coral. 

 Calcareous skeleton if present is derived 



from the basal ectoderm. 

 Types. 

 Actiniaria. Sea anemones. 



Madreporaria. Reef building corals. 

 Antipatharia. Black corals. 



AlcvOnaria, Octocoralla, e.g: 

 Dead Men's Fingers 



All colonial, exxept a small family includ- 

 ing Monoxenia and Haunea. 

 Tentacles eight, feathered, uniform. 



Mesenteries eight, complete. 



Retractor muscles always on one (ventral) 



side of each mesentery. 

 One (ventral) gullet groove or siphono- 



glyphe, or none. 

 Occasional dimorphism among members 



of a colony. 

 There are usually calcareous spicules (of 

 ectodermic origin) in the mesoglo^a. 

 E.xaynples, 

 Alcyoniuni (Dead men's fingers), with 



diffuse spicules of lime. 

 Tubipora (Organ pipe coral), with 

 spicules fused into tubes and trans- 

 verse platforms. 

 CorallhiiJi riibrum (Red coral), with an 



axis of fused spicules. 

 Isis-^ with an axis of alternately Hmy and 



" horny" jolnts. 

 Pen?iatula (Sea pen), a free phosphor- 

 escent colony, with a "horny" axis 

 possibly endodermic. 

 Heliopora^ blue coral. 



Z .A 



Fig. 48. — Z, Diagraiiiniatic section of Zoantharian ; 

 Alcyonarian. (After Chun.) 



The line S—S in Z is through the siphonoglyphes {a). 

 retractor mu.scles are represented by dark thickening. 

 teries— all on one (the ventral) side in Alcyonaria. 



A, of 



The 



on the mesen- 



C(?rrt/il/iZ't?'«^.— We have already noticed that there are "corals"among 

 the Hydrozoa, viz., the Millepores. Leaving these out of account, we 

 have to recognise that both divisions of Anthozoa inchide many corals. 



