1 5 8 



PHYLUM CCELENTERA. 



AMHOZOA OR ACTINOZOA. 



ZOANTHA\IA, HKXACORALI.A, e.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. 

 No dimorphism. 



Calcareous skeleton, if present, isderived 

 from the basal ectoderm. 

 Examples. 



Sea-anemones e.g. , Tea.Ua, and 

 Actinia. 



Madrepore corals many of them reef- 

 building. 



Antipatharians. 



ALCYONARIA, OCTOCORALLA, e.g. 

 DKAD-MKN'S-FIN<;EKS. 



All colonial, except a small family in- 

 cluding Rlonoxenia and Hainiea. 

 Tentacles eight, feathered, uniform. 



Mesenteries eight, complete. 



Retractor muscles always on one (ven- 

 tral) side of each mesentery (see 



Fig- 74). 



One (ventral) gullet groove or siphono- 

 glyphe, or none. 



Frequent dimorphism among members 

 of a colony. 



There are usually calcareous spicules (of 

 ectodermic origin) in the mesoglcea. 

 Examples. 



Alcycnium (Dead-men's-fingers), with 

 diffuse spicules of lime. 



Titbipora. (Organ - pipe coral), with 

 spicules fused into tubes and trans- 

 verse platforms. 



Corallium rul>rum(Red coral), with an 

 axis of fused spicules. 



Pennatula (Sea-pen), a free phosphor- 

 escent colony, with a " horny " axis, 

 possibly endodermic. 



ZOANTHARIA. 



The Zoantharia include many orders, e.g. the primitive 

 Cerianthidea (Cerianthus, etc.) and Edwardsiidea 

 (JEdwardsia\ the Actiniidea including the typical sea- 

 anemones and the Madreporaria, and the divergent Anti- 

 pathidea. The last are colonial, often arborescent, forms 

 with a spinose horny axis on which the small polypes with 

 six tentacles are seated. 



Making of a typical coral. Although the term " coral' 1 

 is applied to many different Coelenterate types with 

 substantial calcareous skeletons, e.g. to Millepores which 

 are Hydromedusas, and to " blue corals " and "red corals ' 

 which are Alcyonarians, the corals par excellence are the 

 Madreporarians. They form the coral rock and "coral 

 islands " found in many parts of the globe, but rarely north 

 or south of a belt extending 30 on each side of the 

 equator, and rarely below the 40 fathom line. 



In a general way a Madrepore polype is like a sea-anemone 



