PHYLUM FORI FEE A 87 



with collared-flagellate cells. Skeleton a framework of inorganic spicul(>s 

 or of organic fibers or both. Aquatic. 



I. Class Calcarea. — Ocean dwellers, in shallow water; chiefly radial 

 in form; spicules of carlwnate of lime, simple or triradiate. 



1. Order Homocoela.- — Gastral epithelium a single sac. Clathrina, 

 Leucosolcnia. 



2. Order Heterocoela. — Gastral epithelium lining canals or 

 chaml^ers around a central cloaca. Gxmjitia, Leucortis. 



II. Class HexactineUida. — Deep-sea forms; chiefly radial in form; 

 skeleton a network of silicious spicules. Hyalonema, Ewplectella. 



in. Class Demospongia. — Marine and fresh water; skeleton of spongin 

 or of silicious spicules or both, sometimes wholly lacking; canal system 

 complicated. 



1. Order Tetraxonida. — Typically tetraxon spicules. Geodia, 

 Plakina. 



2. Order Monaxonida. — Typically simple spicules. Cliona, Sub- 

 erites, SpongiUa, Carterius, Ephydatia. 



3. Order Keratosa. — Spongin; no true spicules. Euspongia, 

 Aplysina. 



4. Order Myxospongia. — Without skeleton. Oscarella. 



References 



(See references cited at close of Chapter I) 



Dendy, a. 1893. "Observations on the Structure and Classification of the 

 Calcarea heterocoela." Quart. Jour. Micr. Set., 35: 159-257. 



Haeckel, E. 1872. "Die Kalkschwamme, eine Monographie." Berlin. 



Moore, H. F. 1908. "The Commercial Sponges and the Sponge Fisheries." 

 Bull. U. S. Bur. Fish., 28: 399-511. 



Parker, G. H. 1910. "The Reactions of Sponges, with a Consideration 

 of the Origin of the Nervous System." Jour. Exp. Zool., 8: 1-41. 



Wilson, H. V. 1907. "On Some Phenomena of Coalescence and Regener- 

 ation in Sponges." Jour. Exp. Zool, 5: 245-258. 



1910. "Development of Sponges from Dissociated Tissue Cells." 

 Bull. U. S. Bur. Fish., 30: 1-30. 



