SPONGES. 113 



solves the spicules leaving the cellular tissue hardened. The 

 decalcified sponge may then be passed through the alcohols 

 and finally cut and mounted as before. 



The spicules may be obtained for mounting by boiling a 

 piece of sponge in potassium hydrate (caustic potash) which 

 dissolves the flesh and sets free the spicules. Then after 

 washing thoroughly allow spicules to settle and pour off the 

 water. The spicules at the bottom may be removed with the 

 pipette and mounted on the slides as other material. 



(2) Study the shape of the entire specimen. Is it sym- 

 metrical? Can you distinguish an upper and lower end? 

 How? Is the sponge attached or free? Is its shape modi- 

 fied to suit this attachment? How? Do you find anything 

 unusual in the shape of any of the specimens ? Can you ex- 

 plain it? Do you find evidences of budding? If so, from 

 what part of the parent sponge does it grow? Explain 

 the process of budding. 



At the upper end look for a large opening, the osculum, 

 surrounded by spicules. Can you tell its use? Do you see 

 anything on the sides which in any way compares with the 

 opening at the end? Do you find spicules on the sides? 

 Put the specimen on a slide and examine with the low 

 power without using cover glass. What do you find? 

 Measure your specimen. Make a large drawing (X3) 

 showing the points studied. 



(3) Cut the specimen longitudinally with the scalpel 

 and examine the internal structure. The osculum at the 

 end should be studied carefully. The internal chamber is 

 the cloaca, or gastral cavity. What is the shape of this cav- 

 ity? How far down does it extend? Does its diameter 

 vary? Study a side of the body wall with the high power. 



STU. IN ZOOL. — 8 



