GRANTIA J 



1. Examine a good-sized specimen of Grantia with the naked eye and 

 note the vase-shaped body with the central opening (osculum) at one 

 end, and the bottom, or base, where the animal was attached to some solid 

 submerged object. Make a drawing in outline, three times normal size, 

 to show the general structure. 



2. Examine the specimen under the dissecting microscope. Note that 

 the body wall is perforated by (a) numerous tiny openings (pores), each 

 of which is surrounded by (6) a cluster of calcareous spicules. Examine 



(c) the larger spicules which surround the osculum. Fill in a portion of the 

 outline made in paragraph 1 with detail showing the nature of the external 

 surface of the body wall. 



3. With a sharp scalpel make a transverse section through the center of 

 the body. Note the large central gastral cavity. Next cut each piece 

 in half in a longitudinal plane noting that the gastral cavity extends the 

 entire length of the body and that the osculum opens directly into it. 



4. Examine a portion of the internal body wall under the low power of 

 the compound microscope with direct illumination. Note (a) that it is 

 perforated with very fine openings (apopyles). Examine a cut surface of 

 the body wall and in a favorable location note two types of parallel canals, 

 namely, (6) the incurrent canals which open to the exterior through the 

 pores previously noted and (c) the radial canals which open into the 

 gastral cavity through the apopyles but do not open to the exterior. 



(d) The openings (prosopyles) between the incurrent and radial canals 

 are too small to be seen. Draw to show the structure of the lining of the 

 gastral cavity and the canals in the body wall as observed. Make a 

 diagram of the animal which will show the course of the water currents 

 through it. 



5. Examine the isolated spicules secured by boiling a Sponge in sodium 

 hydroxide. Note the following types: (a) long rod-like spicules which 

 surround the osculum; (b) short rod-like spicules which surround the 

 incurrent pores ; (c) three-pronged, or triradiate, spicules from the body 

 wall ; (d) T-shaped spicules from the lining of the gastral cavity. Draw 

 to show each type. 



6. Examine a specimen of Grantia which shows asexual reproduction 

 by budding. Draw to show structure as observed. 



7. Examine a bath sponge. Understand that this is simply the skeleton 

 of the animal, composed largely of fibrous spongin. Note the numerous 

 oscula and pores perforating the skeleton. Examine a small piece of a 

 bath sponge under the low power of the microscope to get an idea of the 

 fibrous nature of spongin. 



i B. pp. 52-57. 

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