GRANTIA 77 



cavity has branches? Make a longitudinal sec- 

 tion through the middle of a budded specimen, 

 and note whether a branch of the body-cavity 

 of the parent extends into the bud. 



The body- ■wall. — Examine the longitudinal 

 sections with a low power. N"ote the spicules 

 covering the surface of the sponge, also the 

 whitish sponge flesh, and on the cut surface of 

 the section the longitudinal (radial) canals or 

 incurrent openings running through the wall 

 from the surface toward the cloaca. Are these 

 canals numerous? What is their shape as seen 

 lengthwise and endwise? How are the outer 

 ends of these canals guarded? Are the inner 

 ends likewise protected? Why? Notice the 

 mass of debris among the spicules which cover 

 the surface of the body. In what ways do the 

 flesh and spicules of the bud differ from those 

 of the parent ? Examine transverse sections of 

 the sponge. Do you find that the body-wall 

 projects into the body-cavity in such a way as 

 to subdivide the latter into smaller cavities? 

 Or is it a single continuous cavity ? 



The spicules. — Prepare some spicules as di- 

 rected, and examine under the low power. 

 How many shapes do you find? Draw each 

 kind. Compare with the longitudinal section 

 of the sponge, and note in what part of the 

 body each kind of spicule is found. What is 

 the shape of the spicules found on the surface 

 of the sponge ? Of those embedded in the 

 flesh ? Can you suggest any reasons for these 

 shapes ? Put a drop of hydrochloric acid upon 

 some of the isolated spicules. What is the re- 



