SPONGIARIA 



71 



one and the same phylum inasmuch as they are without a coelom and the 

 hydroid and medusa are usually but stages in the same life history, facts 

 the importance of which had only very recently begun to be understood. 

 Trembley (1744) introduced the term " polypus " because of the fancied 

 resemblance of Hydra to the octopus, the polyp of the ancients. The 

 term "medusa" was employed by Linnaeus and the older writers because 

 of the resemblance of the tentacles of many jellyfish to the snake-like 

 curls of Medusa. 



The phylum is composed of 3 subphyla. 



Key to these subphyla : 



G! Sponges ; animals sessile, without tentacles ................. 1. SPONGIARIA 



o 2 Hydroids, jellyfish, corals, etc. ; no cilia or outer surface ; tentacles usually 

 present ................................................ 2. CNIDABIA 



a a Ctenophores ; outer surface with 8 ciliated bands ; 2 tentacles or none. 



3. CTENOPHOBA 



SUBPHYLUM 1. SPONGIARIA.* (PORIFEEA.) 



Sessile, aquatic ani- 

 mals, with but few spe- 

 cialized organs and tis- 

 sues, in which skeletal 

 fibres or spicules usually 

 form an important part 

 of the body. The animals 

 often live in colonies of 

 irregular form in which 

 the various individuals 

 are indistinguishably fused 

 with one another. Numer- 

 ous pores in the body wall 

 admit water into an in- 

 terior chamber called the 

 cloacal cavity, of which a 

 large opening called the 

 osculum furnishes an outlet. Sponges are without tentacles and motile 

 appendages of any sort and the adult forms have no locomotory 

 powers. 



Fig. 132 Diagrams of the 3 types of sponges 

 (Boas). A, ascon type; B, sycon type; C, leucon 

 type. 1, osculum ; 2, cloaca ; 3, pore canals ; 4 

 radial canal ; 5, flagellate chambers. 



* See "Rep. of Invertebrate Animals of Vineyard Sound and Adjacent Waters," by 

 A. E. Verrill, Rep. of U. S. Fish. Com., 1871. "Poriferata," by A. Hyatt, Stand. 

 Nat. Hist., Vol. 1, 1888. "Spongiaires," by Delage et H6rouard, Traite" de Zool. 

 concrete, 1899. "Sponges," by E. A. Minchen, A Treatise on Zoology, 1900. "Sponges 

 Collected in Porto Rico," by H. V. Wilson, Bull. Fish. Com., Vol. 20, Pt. 2, p. 375, 

 1900. "Catalogue of Recent Marine Sponges of Canada and Alaska," by W. Lambe. 

 Ottawa Naturalist, Vol. 14, 1900. "Biological Survey of Woods Hole and Vicinity," by 

 F. B. Sumner and others. Bull. Bur. Fish., Vol. 31, 1913. 



