- Body with many pores, canals or chambers through which water flows is called the canal system.
- Large aperture called osculum at the upper end.
- Body encloses a large cavity spongocoel.
- No organs, movable parts or appendages. Different kinds of cells perform different functions.
- Usually with an internal skeleton of calcareous or siliceous spicules, or of spongin fibres, or both.
- Reproduction asexual by budding; also sexual.
- Almost all marine.