CHAPTER IX 



SPONGIARIA 

 CALCAREA 



A SYCON SPONGE. GRANTIA 



Grantia is a non-colonial 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 alcohol or 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, needle-like 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 will become, in the course of time, independent animals. 

 Note the evident radial symmetry of the animal. 



Exercise l. 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 pro- 

 jections of ' the central cavity into the body-wall. Examine 

 carefully the cut edges of the body-wall ; observe the radial 



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