SPONGE. 



GRANTIA SP. 



A FEW sponges are found in fresh water, but most are 

 marine; the latter are found in all parts of the world under a 

 great variety of conditions. Grantia is a solitary form, 

 not producing colonies as do many others, though buds at 

 its base may temporarily make a small colony. It is per- 

 manently attached to rocks, piles and sea-weed below low- 

 water mark. 



I. External Anatomy. 



Place a specimen in a watch glass in water or alcohol. 

 Observe the form of the animal, and its mode of attach- 

 ment. At the free end note the opening, the osculum, 

 partly covered and protected by a cluster of spicules. This 

 opening is not a mouth, but an excurrent opening for the 

 discharge of water from the animal. In the sides of the 

 animal are many minute openings, the incurrent pores or 

 ostia. Are these covered or protected by spicules like the 

 osculum? 



Make a drawing of a specimen. 



II. Internal Anatomy. 



With a razor cut a dry specimen longitudinally and ex- 

 amine the section with a lens. Observe the central cavity 

 and the small pores, the apopyles, which pierce its wall. In 

 the walls find a series of canals arranged in radial fashion. 



