168 



COELEXTERATA. 



Toxochjtus L. Ag. ; Lyclmorliiza H. ; Phyllorhiza L. Ag. ; Eupilcma H. ; Pilema 

 H. ; Rhopilema H. ; Brachiolophus H. ; Stomolophus L. Ag. 



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

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

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

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

 rhiza H. 



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

 portions, oral arms with dorsal and ventral frills. 8 rhopalia ; 8-16 or more 

 anastomosing radial canals ; usually a circular canal. G'rambessa H. ; Mastigias 

 L. Ag.; Eucrambessa H. ; Thysanostoma, L. Ag. ; Himantostoma L. Ag. ; Lcpto- 

 brach-ia Brandt ; Leonura H. 



Class III. ACTINOZOA* (ANTHOZOA). 



Polyps colonial or solitary, -iritJi oesopliageal tube, mesenteric folds, 



and endodermal yonads. A medu- 

 soid sexual generation is unknown. 



The polyp of the Adinozoa 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 Avhich the free ends of the polyps project. A calcareous 

 skeleton is very generally present, but its form and method <>f 

 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, " Beitriige zur physiologischen Kenntniss der Korallenthiere im 

 Allgemeinen u. besonders des rotten 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, Histoirc Naturelle des Coraillaires, 3 vols. , 

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



FIG. 138. Branch of a polyparium of 

 Coralliam rubrum (after Lacaze Du- 

 thiers). P polyp. 



