STRUCTURE AND FUNCTION 53 



4. Although individual cells are sensitive, a sponge as a 

 whole is not. What connection has this fact with the fact 

 that sponges are stationary ? 



5. Compare simple and complex sponges. 



Suggested drawings. 



a. A view of a simple sponge. Label everything shown. 



d. A diagram of a simple sponge split in halves. Show 

 by arrows the path followed by the water as it passes 

 through the sponge. 



c. A few spicules. 



d. A few fibers. 



Summary of Important Points in the Study of Sponges 



1. What are two functions of the spicules or fibers.-' 



2. What are at least two of the functions of the en- 

 doderm cells ? 



3. What can you suggest as functions for the ectoderm 

 cells } 



4. In what cases do cells show " team work " in accom- 

 plishing an object.' 



5. What degree of specialization is indicated by the fact 

 that the cells may exchange positions and functions.' 



6. What work can any single cell of a sponge do .-• 

 Compare the work done by such a cell with that done by a 

 Paramecium. 



7. What work can a whole sponge do .■' Compare that 

 with the work done by a Paramecium. 



Review and Library Exercise on Sponges 



1. What are the distinguishing characteristics of Porif- 

 era ? 



2. Sponges were once supposed to be plants. In what 



