168 



COELENTERATA. 



Toxoclytus L. Ag. ; Lychnorhiza H. ; Phyllorhiza L. Ag. ; Eupilema H. ; Pilema 

 H. ; PJiopilema H. ; Brachiolophus H. ; Stomolophus L. Ag. 



Fam. 15. Versuridae. Rhizostomae with a single central subgenital porticus 

 (i.e., subgenital pits united), with ventral suctorial oral frills only. 8 rhopalia; 

 8-16 or more narrow, branched, anastomosing, radial canals. Haplorhiza H. ; 

 Cannorhiza H. ; Versura H. ; Crossostoma L. Ag.; Cotylorhiza L. Ag. ; Stylo- 

 rhiza H. 



Fam. 16. Crambessidae. Rhizostomae with a single central subgenital 

 porticus, oral amis with dorsal an*d ventral frills. 8 rhopalia ; 8-16 or more 

 anastomosing radial canals ; usually a circular canal. Crambessa H. ; Mastigias 

 L. Ag. ; Eucranibessa H. ; Thysanostoma L. Ag. ; Himantostoma L. Ag. ; Lepto- 

 brachia Brandt ; Leonura H. 



Class III. ACTINOZOA* (ANTHOZOA). 



Polyps colonial or solitary, with oesophageal tube, mesenteric folds, 



and endodermal gonads. A medu- 

 soid sexual generation is unknown. 



The polyp of the Actinozoa has 

 already been described (p. 102). It 

 differs from that of the Hydro- 

 medusae in being larger, in having 

 a greater muscular development, a 

 .better developed structureless la- 

 mella or jelly which often contains 

 muscular and skeletal elements. The 

 development of this jelly, which has 

 a tough, dense character, is, in the 

 colonial forms, greater in the lower 

 parts of the polyps than in the 

 upper, the result of which is the 

 formation of the branched or massive 

 coenenchyme (Fig. 138), from the 

 surface of which the free ends of "the polyps project. A calcareous 

 skeleton is very generally present, but its form and method of 

 formation vary in the different groups. 



The mesenteries and tentacles vary much in number. In the 

 Alcyonaria there are always eight; in the Zoantharia, in which there 

 are primary and secondary mesenteries, the number is sometimes six 



* Ehrenberg, "Beitrage zur physiologischen Kenntniss der Korallenthiere im 

 Allgemeinen u. besonders des rothen Meeres, etc," Abhand. d. Berliner Akad., 

 1832. Ch. Darwin, The Structure and Distribution of Coral Reefs, London, 

 1842. J. D. Dana, United States Expl. Expedition, Zoophytes, Philadelphia, 

 1846. M. Edwards and J. Haime, Histoire Naturelle des Coraillaires, 3 vols., 

 Paris, 1857-60. Lacaze Duthiers, Histoire Naturelle du Corail, Paris, 1864. 



FIG. 138. Branch of a polyparium of 

 Corallium rubrum (after Lacaze Du- 

 thiers). P polyp. 



