Phylum Porifera ("pori" = pores, "fera" = bearers) popularly known as sponges, a group simple organisms. Sponges are sessile organisms found attached to a substratum.
The majority of sponges are marine, living in seas and oceans. There is one family of fresh water sponges (Family Spongillidae).
Unlike Protozoans, the Poriferans are multicellular. However unlike higher metazoans the cells that make up a sponge are not organised into tissues. Primarily their body consists of a thin sheet of cells over a frame (skeleton).
As their name suggests, Poriferans are charecterized by the presence of minute pores called ostia on their body and One large opening hole like structure called Oscullum . Poriferans body have consist many ostia in numbers but oscullum are one .