The phylum Porifera. The most primitive of the multicellular animals, lacking any organs or tissues. They consist in principle of a structure of cells with pores, arranged around a spongocoel or lumen, and supported by a primitive connective tissue, containing skeletal spines (calcareous or siliceous or spongine fibers). Through the pores, water with oxygen and food is pumped from the outside into the spongocoel, from where it leaves the sponge. There is no organization in the activities in sponges; any part of the body can regenerate. They are hermaphrodites. They live sessile in marine and freshwater.