Sclerocytes and Spongocytes secrete substances that make up the central matrix of these creatures, and the outer layer of these creatures is made from pinacocytes.  These creatures are defended by silicate projections called spicules, and the central excretory structure is the osculum.  Members of this phylum appear in asconoid, synconoid, and leuconoid body types, and their digestive systems are composed of rings of microvilli with interspersed collar cells.  Made of a central matrix called the mesohyl, these creatures belong to the classification parazoa because they are thought to contain no tissues. For 10 points, name these simple organisms, also known as sponge
Sclerocytes and Spongocytes secrete substances that make up the central matrix of these creatures, and the outer layer of these creatures is made from pinacocytes.  These creatures are defended by silicate projections called spicules, and the central excretory structure is the osculum.  Members of this phylum appear in asconoid, synconoid, and leuconoid body types, and their digestive systems are composed of rings of microvilli with interspersed collar cells.  Made of a central matrix called the mesohyl, these creatures belong to the classification parazoa because they are thought to contain no tissues. For 10 points, name these simple organisms, also known as sponges.
Sclerocytes and Spongocytes secrete substances that make up the central matrix of these creatures, and the outer layer of these creatures is made from pinacocytes.  
{Porifera} [or {Sponges} before mention]