PORIFEEA. 15 



Of what mineral substances are these spicules ? 

 (Dem.) 



2. A FRESH-WATER SPONGE. Spongilla. 



A. Habitat. (Dem.) 



1. Where were these sponges collected ? 



2. If you were collecting, where would you look for 



the fresh-water sponges and how would you rec- 

 ognize them ? 



B. The Liiving Sponge. 



1. Has the sponge any definite form ? (Examine sev- 



eral specimens.) 



2. What is the appearance of the sponge " flesh " ? 



3. Have the spicules a definite arrangement ? 



4. Of what mineral substance are these spicules ? 



(Dem.) 



5. Identify the oscula. 



Would you call this sponge a colony or an individual? 



C. The Spong-e "Flesh." 



1. Identify the cells which form the sponge flesh. (Dem.) 



2. In what respect do these cells resemble Amoebse ? 



3. Do they form a tissue ? 



D. Drawings. 



1. A sponge colony. 



2. A sponge cell. (1 cm.) 



3. Spicules. 



3. A TOILET SPONGE. Skeleton of Euspongia. 



1. Test the elasticity of the skeleton by squeezing it. 

 (Use both dry and wet specimens.) 



