Poriferans are commonly referred to as sponges. Fossil sponges are among the oldest known animal fossils, dating from the Late Precambrian. There are approximately 5,000 living species of sponges. These organisms do not have mouths, but have tiny pores in their outer walls, in which water is pumped into the body. The flow of water is unidirectional. Sponge cells perform a variety of bodily functions and appear to be more independent than any other cells of other animals,