DEMOSPONGIAE
There are many diverse Orders in this class, which include all of the large sponges. the majority of these are marine dwellers, but many live in freshwater environments. a few species are brightly colored, and there is a great variety in body shape. the largest species are over 1 meter (3.3 ft) long. Demospongiae is the largest Class in the Phylum Porifera. One great example of demospongiae is the brown tube sponge -found on the right-. Their "Skeletons" are made of Spicules that consist of fibers of the protein spongin, the mineral Silica or both. The spicules are either simple or four-rayed. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. All demospongiae have the leuconoid canal system. the spongin provides a matrix in which the spicules are embedded. The Demospongiae vary in size from small, encrusting forms to very large, irregular masses.