196 



MESOZOA THROUGH ENTOPROCTA: 



Some Spicule Types 



Simple Sponge Organization 



CLASS CALCAREA ( = CALCISPONGIAE) (Calcareous 

 Sponges) 



Diagnosis: typically solitary or colonial vase- 

 shaped organisms; some form bushy or compact 

 masses, and a few have stalk-like bases; spicules of 

 calcium carbonate and usually causing a bristly sur- 

 face; mostly drab, inconspicuous animals less than 

 6 inches long; strictly marine organisms occupying 

 intertidal to 3000-foot waters, are most likely found 

 in tidepools either on rocks or within cracks and 

 crevices in rocks, or on marine algae (kelp) hold- 

 fasts (root-like structures) (Figure 12.4). 



CLASS HEXACTINELLIDA ( = HYALOSPONGIA) 

 (Glass Sponges) 



Diagnosis: spicules glassy or siliceous, and six- 

 rayed; mostly solitary, cylindrical, vase-, urn-, or 

 funnel-shaped animals, but some are curved, flat- 

 tened, or branched; most are 4 to 12 inches long; but 

 some are 3 feet long; strictly marine, from 300 feet 

 to 3 miles deep (Figure 12.4). 



CLASS DEMOSPONGIA (Frame Sponges) 



Diagnosis: three subclasses: Tetractinellida, a 

 shallow-water marine group, lack fibrous spongin and 

 either lack spicules or have four-rayed siliceous ones; 

 Monaxonida, a mostly shallow-water, marine group, 

 but extend to over 3-mile depths and include a fresh- 

 water family; possess toothpick-like siliceous spicules 

 and some have spongin; Keratosa, usually a shallow- 

 water, hard marine bottom group, strictly marine, 

 include the bath or commercial sponges; skeletons all 

 fibrous spongin (Figure 12.4). 



Figure 12.3 Sponge structure. 



ferred by the amoeboid cell to an egg to effect fertili- 

 zation. Development in part resembles that of cer- 

 tain colonial flagellate protozoans. 



Regeneration of parts is found in many parts of 

 the animal kingdom, but no other animals can 

 match the amazing powers of the sponges in this 

 respect. One may separate the cells of a sponge by 

 straining them through fine cloth. In a suitable 

 medium, whenever a sufficient number of cell types 

 get together, the cells reorganize to form a new 

 sponge. 



RADIATA: 

 COELENTERATA AND CTENOPHORA 



The body plan and organization of the Mesozoa 

 and Porifera are based directly on the cell. We now 

 approach another type of complexity, animals whose 

 differentiation can be summed in the tissue. Two 

 phyla, the Coelenterata and the Ctenophora, display 

 this organization. These and all the remaining phyla 

 are members of the Subkingdom Eumetazoa; however 

 all except the Radiata possess definite organs. The 



