CLASSIFICATION OF CCELENTERATA. 143 



(f) The Hydroid colonies known as Plumularians and Sertularians 

 have no free medusoids. 



(d) The divergent Hydrocorallinse, e.g., Millepora and Stylaster, 



with calcareous skeletons, seem to have gonophores. 



(e) On the other hand, the Trachymedusje exist only as medusoids, 



e.g., Geryonia, Carmarina, Cunina. Aeginojl>sis. 

 3. Order Siphonophoroe. Free-swimming colonies of modified medus- 

 oid persons (medusomes) with much division of labour. 

 e.g. Physalia (Portuguese Man-of-War) and Diphyes ; 

 Vellela and Porpita. 



B. Class ScYPHOzoA. 



There are tv?o types — polypoid and medusoid — very rarely 

 occurring in one life-history. The gastric cavity has partitions 

 with gastric or mesenteric filaments, and there is more or 

 less of an ectodermic gullet. The mesogloea generally con- 

 tains migrant cells. The reproductive cells are endodermic. 



I. Sub-Class ScyphomedusEe or Acraspeda — 



Jellyfish with gastric filaments, sub-genital cavities, no velum, 

 etc. (see before). These are classified in various ways : — 

 StauromedusEe, e.g., Lucernaria ; PeromedusEe, e.g.. Peri- 

 colpa ; Cubomedusee, e.g. , Charybdea ; Discomedusae, e.g. , 

 Aurelia, Cyanea, Pelagia, Pilema or Khizostoma. 



Pelagia develops directly without polypoid stage. 



Aurelia passes through Scyphistoma and Strobila polypoid stage. 



Lucernaria is sedentary, and fixes itself by a stalk. It thus 

 resembles Anthozoa in habit as well as in structure. 



II. Sub-Class Anthozoa or Actinozoa — 



Polypoid, with well-developed gullet and mesenteries, with 

 circum-oral tentacles, etc. (see before). 



a. Zoantharia. 



Actiniaria. Sea-Anemones, e.g.. Actinia, Anemonia, 

 Tealia, Cereantkus, etc. 



Madreporaria. Stone or reef corals, e.g., Astrcea, 

 Madrepora, Fungia, Mceandrina. 



Antipatharia. So-called black corals, with a horny axial 

 skeleton, and occasional dimorphism between nutri- 

 tive and reproductive " persons," e.g., Antipathes. 



b. Alcyonaria, e.g., Alcyonium (Dead-men's-fingers). 

 Tubipora (Organ-pipe coral), Coralliuvi (Red coral), Gorgonia, Pen- 



natula (Sea-pen), Monoxenia (non-colonial). 

 Among the Anthozoa are also included the extinct or almost entirely 

 extinct Rugose corals (Tetracoralla), with numerous septa in some 

 multiple of four. 



