164 



PHYLUM CCELENTERA. 

 ANTHOZOA OR ACTINOZOA 



ZOANTHARIA, HEXACORALLA, e.g. 



SEA-ANEMONE. 



ALCYONARIA, OCTOCORALLA, e.g. 

 DEAD-MEN'S-FINGERS. 



Many are simple, many colonial. 



The polyps of a colony may give rise 



to others directly by fission or 



budding. 

 Tentacles usually simple, usually some 



multiple of six, often dissimilar. 

 Mesenteries usually some multiple of 



six, complete and incomplete. 

 Retractor muscles never as in Alcyo- 



naria. 



Two gullet grooves or siphonoglyphes, 



or only one. 

 No dimorphism. 



Calcareous skeleton, if present, is derived 

 from the basal ectoderm. 



Examples. 



Sea - anemones e.g. Tealia and 

 Actinia. 



Madrepore corals, many of them reef- 

 building. 



Antipatharians. An aberrant Anti- 

 pathar ian , Dendrobrach ia fallax^ 

 has eight feathered tentacles. 



All colonial, except a small family in- 

 cluding Monoxenia and Haimea. 



The polyps of a colony give rise to 

 others not directly, but through 

 stolons or solenia. 



Tentacles eight, feathered, uniform. 



Mesenteries eight, complete. 



Retractor muscles always on one (ven- 

 tral) side of each mesentery (see 

 Fig. 81). 



One (ventral) gullet groove (siphono- 

 glyphe or sulcus), or none. 



Frequent dimorphism among members 

 of a colony. 



There are usually calcareous spicules (of 

 ectodermic origin) in the mesogloea. 



Examples. 



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

 diffuse spicules of lime. 



Tubipora (Organ - pipe coral), with 

 spicules fused into tubes and trans- 

 verse platforms. 



Corallium rubrum (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 primi- 

 tive Cerianthidea (Cerianthus^ etc.) and Edwardsiidea 

 (Edwardsia\ the Actiniidea (including the typical sea- 

 anemones and the Madreporaria), and the divergent Anti- 

 pathidea. 



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

 is applied to many different Ccelenterate types with 

 substantial calcareous skeletons, e.g. to Millepores which 

 are Hydrozoa, 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 4o-fathom line. 



