CHAPTER XL 



PHYLUM II. PORIFERA. 



LABORATORY EXERCISES. 



199. Grantia. This is a marine sponge and in consequence 

 the majority of schools will be compelled to depend upon alco- 

 holic material. Grantia occurs along our New England coast, 

 and is found attached to piles or to stones a few feet below the 

 low-tide mark. If the school is near the coast the living sponge 

 should be studied in a basin of sea-water. 



1. General Form. (Keep in a watch-glass, covered with 

 the preserving fluid.) Make careful outline sketches of every- 

 thing discovered. 



Note, the basal or attached portion; the column; the free 

 end. How do the ends differ? Are there any openings? 



Do you find any connection between individuals (budding) ? 

 Are these individuals of equal size? 



2. Structure. Split the body longitudinally with a sharp 

 scalpel, and examine with hand lens or a low power of the 

 microscope. 



Study, body wall; cloaca (internal cavity) ; the relation 

 of the cloaca to the osculum (the opening at the unattached 

 end). 



By what is the osculum surrounded? Notice in the wall of 

 the cloaca the minute openings of the radiating tubes. Do 

 they communicate with the exterior? What are the functions 

 of the osculum and of the pores? Evidences? 



3. Make thin cross sections with a razor, mount under cover-glass, and 

 examine further for points in 2. Notice the spicules. Is there any regu- 

 larity in their arrangement? What differences in shape and size have 

 you discovered in the spicules from different regions of the body? 



4. Place a bit of the sponge in a small amount of a 5% solution of 

 caustic potash and boil. Examine under high power, and draw the dif- 

 ferently shaped spicules. 



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