MARINE AQUARIA 



II. Coelenterata. I 



find a place in this book. Only the most common littoral forms, those 

 living on or near the shore, are mentioned and those of greatest interest 

 to the collector are described. The Marine fauna may be roughly classed 

 as: — 



I. Porifera. Sponges. 



Polyps, etc.. Seaweedlike Zoophytes and small Jellyfishes, some 

 of the Corallines, and Hydrozoa generally. 

 Larger Jellyfishes and Scyphozoa generally. 

 Sea-anemones, Actinoid corals and Actinozoa generally. 

 ^ Comb-jellies and Ctenophora generally. 



III. Vermes. Worms and Leeches. 



IV. MoUuscoida. Sea-mats or Polyzoa, and Corallines or Brachiopods. 

 Starfishes, Brittle-stars, Sea-urchins, Sea-cucumbers, Feather- 

 stars, Sea-lihes and Radiates generally. 



I Crustaceans, Entomostraca, Barnacles, Lobsters, Shrimps, etc., 



VI. Arthropoda. \ King Crabs, Sea Spiders, Squilla, and the Amphipods and Iso- 



I ■ 

 1^ pods in general. 



f Limpets, Tops, Whelks, Periwinkles and other Gasteropods ; 

 VII. MoUusca. \ Mussels, Clams, Scallops and Pelecypods generally. 



1^ Cuttles and other Cephalopods. 

 VIII. Chordata. Sea Squirts and allied forms. 



IX. Pisces. Fishes. 



V. Echinodermata. 



Porifera or Sponges. These constitute one of the lowest forms 

 of animal life, propagating by gemmation or budding. The sponge of 

 commerce is the skeleton or framework, the organic portion being a soft 

 and jellylike substance of which the external layer is composed of fiat cells 

 with numerous pores and larger openings for inhaling and straining the 

 water; the middle layer of cells having various functions, as the formation 

 of the framework, digestion and reproduction; and the internal layer of 

 cylindrical cells leading to sacs, each having a fiagellate hair to create a 

 current. These take in the food, digest it and eject the excrement. 

 Almost every seaweed, rock, mollusc and crab has some member of this 

 family attached to it, which vary in size from tiny specks to large and sub- 

 stantial masses of varying forms and colors. Sponges are roughly divided 

 into two classes, Calcarea and Non-Calcarea. 



The genera most usually met with are the following, of which a brief 

 description will suffice, as they do not survive in the marine aquarium. 



DusEiDEiA, having an imperfectly cellular body composed of a gela- 

 tinous membrane covered with amorphous particles of sand. 



Grantia, having a firm, elastic body with calcareous spicula com- 

 pacted in a gelatinous base. 



299 



