Branch Porifera 17 



a. The general outline of the body, with its surface 

 roughened by the presence of innumerable spicules. 



b. Beneath the rough surface of the spicules see the 

 inhalent pores, scattered thickly over the wall of 

 the sponge. 



c. The expansions at the basal end by which it is 

 attached to the object upon which it grows. 



d. The terminal osculum, the opening at the upper or 

 distal end surrounded by a funnel-like circlet of 

 spicules. 



II. — Make with a sharp scalpel a longitudinal section of 

 the sponge. Observe : — 



a. The central cavity into which the osculum opens; 

 this cavity is called the cloaca. 



b. The many minute openings through the inside wall 

 of the sponge are called the gastric ostia. 



c. In the cut surface of the sponge the numerous 

 parallel canals, which connect the inhalent pores 

 with the ostia. Make a diagrammatic drawing 

 showing the structure of the sponge when thus 

 seen in a longitudinal section. 



III. — Mount some of the spicules from the inside and out- 

 side of the sponge and examine with compound micro- 

 scope. Is there any difference in the appearance of 

 those from the two situations .>' Draw specimens of each. 



This is an example of sponge life. The body is supported 

 by the skeleton of spicules. Water containing microscopic 

 plants or animals which serve as food is drawn through the 

 inhalent pores into the parallel canals, where some of the 

 food particles are taken up by certain cells. Then the water 

 goes on through the ostia into the cloaca, and later passes 

 out through the large osculum. 



