24 



SPONGES 



From these the apopyles open into the primary radial canal, which is in com- 

 munication with the gastral cavity. Thus water enters through the ostia ; 



Primary Radial Canal 



Secondary Radial Canal 

 "* or Radiating Chamber 



'Primary Inhalent Canal 



ProBopyle 

 Middle Jelly 



Apopyle 

 Dermal Epithelium 



Flit. 9. — Transverse Section of a Rliagon Sponge. From Masterman's 

 Text-book of Zoology. 



thence by the prosopyles into the secondary radial canals ; and from these by 

 the apopyles into the primary radial canals, and so into the gastral cavity. 

 Example : Oscarella (Class, Demospongise ; Order, Myxospongida). 



