SURVEY OF CCELENTERA 205 



according to the position of the gonads. Examples : Geryonia, Car- 

 marina, Cunina, Aeginopsis. (Tlie fresh-water medusoid Limnocodiutn 

 or Craspedacusta is budded oft" from the North American Microhydra 

 ryderi). 



2. Order Siphonophora. — Free-swimming colonies of modified 

 medusoid persons (medusomes), with much division of labour. 



Physalia (Portuguese man-of-war), Diphyes, Velella, Porpita. 



Incertce sedis. Graptolites. — Extinct unattached colonies with a 

 rod-like axis found in Upper Cambrian, Ordovician, and Silurian 

 systems. The colony is usually linear, and consists of cup-shaped 

 hydrothecae borne on one, two, or four sides of the solid axis {virgula). 

 Each opens into a common median canal. At the proximal free end 

 there is a minute triangular or dagger-shaped body — the sicula — 

 which represents the embryonic skeleton. Some reproductive bodies 

 or gonangia have been found. The animals were probably free- 

 swimming in muddy seas, and of a Hydromedusan nature. 



Class II. ScYPHOMEDUS^ ( = Acraspcda) 



Jelly-fish with gastric filaments, sub-genital pits, and no velum — 

 (i) Lucernariae. — Sedentary forms. Lucernaria, Haliclystus, and 

 Depastrum. 



(2) Discomedusae. — Active forms, often with complicated life- 



history. Aurelia, Pelagia, Cyanea, Rhizostoma. 



(3) Cubomedusae. — Forms with broad pseudo-velum, and other 



peculiar features. Charybdea. 



(4) Peromedusse. — Forms with four inter -radial tentaculocysts 



only. Pericolpa. 



Class III. Anthozoa (=Actinozoa) 



Polypoid forms with well-developed gullet and septa, and circumoral 

 tentacles, 

 (i) Zoantharia or Hexacoralla. 



{a) Actiniaria. Sea-anemones. Actinia, Anemonia, Tealia, 



Cerianthus. 

 {b) Madreporaria. Stone or reef corals. 



Asircsa, Madrepora, Fimgia, McBandrina. 

 (f) Antipatharia. " Horny " black corals. Antipathes. 

 (a) Alcyonaria or Octocoralla. 



Alcyonium (Dead-men's-fingers), Tubipora (Organ-pipe 

 coral). Cor allium (Red coral)," Sea- fans, Pennatula (Sea- 

 pen), Monoxenia (non-colonial). 



Class IV. Ctenophora 



Delicate free-swimming organisms, generally globular in form, 

 moving by means of eight meridional rows of ciliated plates, or comb- 

 like combinations of cilia. The stinging cells are almost always 

 replaced by " adhesive cells." The mouth is at one pole, and leads 



