CHAPTER XVI 

 BRANCH PORIFERA: THE SPONGES 



THE FRESH-WATER SPONGE (Spongilla sp.) 



TECHNICAL NOTE. Fresh-water sponges may perhaps not be 

 readily found in the neighborhood of the school, but they occur 

 over most of the United States, and careful searching will usually 

 result in the finding of specimens. They are compact, solid-looking 

 masses, sometimes lobed, resting on and attached to rocks, logs, 

 timbers, etc., in clear water in creeks, ponds, or bayous. They 

 are creamy, yellowish-brown or even greenish in color and resemble 

 some cushion-like plant far more than any of the familiar animal 

 forms. They can be distinguished from plants, however, by the 

 fact that there are no leaves in the mass, nor long thread-like fibres 

 such as compose the masses of pond algae (pond scum). When 

 touched with the fingers a gritty feeling is noticeable, due to the 

 presence of many small stiff spicules. Sponges should be removed 

 entire from the substance they are attached to, and may be taken 

 alive to the laboratory. They die soon, however, and should be put 

 into alcohol before decay begins. 



Note the form of the sponge mass. Is it lobed or 

 branched ? Examine the surface for openings. These 

 are of two sizes'; the larger are osteoles or cxhalant open- 

 ings, while the smaller and more numerous are pores or 

 inJialant openings. The sponge-flesh is called sarcode. 

 Examine a bit of sarcode under the microscope ; note the 

 spicules. Have these spicules a regular arrangement ? 

 Of what are they composed ? 



Draw the entire sponge, showing shape and openings ; 

 draw some of the spicules. 



Embedded in the body-substance, especially near the 

 base, note (if present) numerous small, yellowish, sub- 



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