14 STUDIES OF ANIMAL LIFE. 



C. The Canal System. 



The body of the sponge is penetrated by a system of 

 canals and cavities for the passage of water. 



1. The Osculum, a large opening at the distal end of 



the body. 



2. The Central Cavity. (Examine a sponge split length- 



wise and one in cross-section.) 

 a. What is the relation of the central cavity to the 

 osculum ? 



3. The Canals, small passages through the body wall 



leading from the outer surface to the central 

 cavity. 



4. The external openings of these canals are called 



inhalent pores, and the internal openings into the 



central cavity are called ostia. Identify the canals 



and their openings. 

 What causes the water to flow through the canals ? ^ 

 What is the course of the water through the canals ? 



Show this by arrows in the diagram for C 5. 



5. Make a clay model of a sponge split lengthwise 



(8 cm.). 



6. Make a drawing or diagram (4 cm.) of a sponge 



split lengthwise, to show the relation of the dif- 

 ferent parts of the canal system to one another. 

 Label fully. (See Laboratory Axiom 2.) 



D. Spicules. 



1. Are the spicules arranged in regular order in any 



part of the body ? (1. and l.p.) 



2. Draw perfect examples, much enlarged, of the dif- 



ferent shapes you find. (Dem.) 

 What is the use of spicules to the sponge ? 

 1 See footnote on p. 7. 



