Sycon is a sedentary sponge. It leads an aquatic life The body of sycon shows pores and canals which form a complex canal system. It is called sycon type of canal system. It is useful to draw water current inside the body. These water currents bring in food and oxygen. The body wall of sycon contains outer dermal layer and inner choanoderm. in between these two layer mesenchyme is present. The body wall is folded regularly and develop a regular canal system.

1) Ostia : The body wall is folded. In between two folds an incurrent canal is present. The opening of incurrent canal shows a pore membrane. This will show one or two ostia, through which water enters into the incurrent canals. The ostium is surrounded by myocytes. These amoebocytes will work as sphincters. They can close these openings or open them to regulate the inflow of water.

2) Incurrent canals : In between two folds of the body wall an incurrent canal is present. These canals end blindly towards inside. This is lined inside by pinacocytes. These are flat cells and are contractile.

3) Prosopyles : The incurrent canal opens into the radial canal through prosopyles'.

4) Radial canals: In between two incurrent canals a radial canal is present. It ends blindly to the exterior. It leads into excurrent canal internally.

Radial canal is lined with choanocytes or flagellated cells. Hence these chambers are called flagellated chambers.

5) Apopyle : Radial canal opens into excurrent canal through an opening called apopyle. The apopyle is also surrounded by Myocytes.

6) Excurrent canal: It is short and wide chamber. It opens into spongocoel. This canal is lined with flat epithelial cell like the spongocoel. The board opening between excurrent canal and sponogocoel is also called internal ostium.

7) Spongocoel: The central part of the cylinder of sycon will show a hollow cavity called spongocoel. it is lined with epithelial cells. At the apex it opens out through osculum.

Because of the action of flagella of choanocytes water is drawn into the body. This is called incurrent water. This brings in food and oxygen. Hence it is called nutritive current. The water that goes out of the osculum is called excurrent water.

Functions of Sponge Canal System :

1) It brings constant supply of water into the body and helps in respiration.

2) Water brings with in small food particles which are used by the sponge

3) It helps in the process of reproduction.

4) It helps in the process of discarding waste matter out of the body.