SKELETON OF TOILET SPONGE 6V 



and note the change. How do you account for 

 it ? Is a wet sponge more elastic than a dry one? 

 Soak a sponge thoroughly in water, then squeeze 

 out as much as possible of the water into a dish 

 and measure the amount. 



e. Structure. 



1. The oscula (large openings on the upper sur- 



face of the sponge). — How many on your spec- 

 imen ? "What is their shape ? Size ? Note 

 that each osculum is the outlet of a canal 

 which runs down into the body of the sponge. 

 Look down into an osculum and notice the 

 numerous smaller canals which open into the 

 large one. Notice also that the skeleton be- 

 comes thinner and less compact at the margin 

 of the osculum. 



2. The canals. — With a sharp knife or a pair of 



scissors cut through the skeleton so as to 

 divide at least one of the large canals length- 

 wise. How far into the body does the canal 

 penetrate ? Does it decrease or increase in size 

 as it approaches the osculum ? Do any of the 

 large canals unite directly or are they connect- 

 ed by smaller canals ? Do the walls of the 

 canals have the same appearance as regards 

 smoothness, texture, color, etc., as the surface 

 of the skeleton ? 

 Make outline drawings showing the sponge as seen 

 from the side and from the top, indicating the posi- 

 tion of all of the large oscula ; also a drawing of a 

 section showing the course of some of the principal 

 canals. 



3. The fibres. — Look closely at the surface of the 



