- SIZE AND SHAPE OF SYCON SPONGE: The colony contains groups of cylinders, which are branched. Each cylinder grows three inches in length. All the branched cylinders are connected to a base. At the apex of the cylinder an opening is present called oseulum. Around this opening monaxon spicules are arranged in a circle, called oscular fringe.
- Colour : The body shows many colours from grey to brown shade.
- Pinacocytes : These are simple flat, polygonal cells. These are highly contractile. They cover the entire outer body surface of the sponge. Pinacocytes covering the outer body surf fromthe dermalepithelium and which cover paragastric cavity and form the gastral epithelium.
- Potocytes :These are tubular cells distributed among the pinacocytes. They form the openings on the dermal layer.
- Choanocytes : These are round cells. They show big nucleus A long flagellum s rises from each cell. At base of the flagellum a protoplasmic collar is present. The action of flagellum brings in water. This cell is useful in digestion, respiration and other functions.
ii) Silicoblasts: Scleroblasts that secrete silicious spicules
- Large one rayed needle like Monaxon spicules,
- Simple monaxon spicules project from dermal layers on the walls of the radial canals,
- Triaxon spicules are present on the walls of spongocoel.
- Tetraxon spicules are present on the walls of spongocoel.