Demosponges of the class Demospongiae are the most numerous of the sponges containing 90 to 95 percent of Porifera species. They are typically brightly colored and range in size from a few millimeters to several meters. Demosponges are asymmetrical forming a variety of shapes including tube-like, cup-like, and branched shapes. Like glass sponges, they have leuconoid body forms. Demosponges are characterized by skeletons with spicules composed of collagen fibers called spongin. It is the spongin that gives sponges of this class their flexibility. Some species have spicules that are composed of silicates or both spongin and silicates.