PHYLUM PORIFERA.>j. 



Class: Calcarea v^ ^ \^ 



A SPONGE (GRANTIA) 



Grantia is a noncolonial sponge which is common along the 

 New England coast. It is a small, cylindrical animal, about half 

 an inch in length, and occurs in small groups attached to rocks 

 or other objects below low-water mark. 



Place several specimens in a watch glass of water, and study 

 their shape and external characters with the aid of a hand lens. 

 Observe the cylindrical body and at one end of it a small opening 

 surrounded by straight, needlelike spicules ; the opposite end is 

 the one by which the animal was attached. The opening is called 

 the osculum or excurrent opening. Notice the smaller spicules 

 and the openings of numerous minute pores which cover the sides 

 of the body. Growing out from the base of the larger individuals 

 may often be seen small ones, which in the course of time will 

 become independent animals. Note the evident radial symmetry 

 of the animal. 



Exercise 1. Make a drawing of an animal on a scale of 5. 



Split a dried sponge with a sharp knife into two equal halves 

 and study it under a dissecting microscope. Observe the large 

 central cavity. Large numbers of openings will be seen in its wall ; 

 they are the mouths of the radial canals, which are projections of 

 the central cavity into the body wall. Examine carefully the cut 

 edges of the body wall ; observe the radial canals, which are cut 

 longitudinally here. Notice also the shorter and less regular in- 

 current canals, which lie between the radial canals and open to 

 the outside through external incurrent pores. There are thus two 

 systems of canals in the body wall : (i) the radial canals, which 

 are a part of the central cavity, and (2) the incurrent canals, 



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