The glass sponges get their name from their skeleton that is made of small rods or long, bristle-like fibers (spicules) made of silica, or glass. The sponge makes the glass with silicic acid it extracts from the seawater. Each spicule is a little spiny cluster consisting of four or six rods at right angles to each other, like a shape you could build with Tinker Toys. The fused spicules create a lattice structure that forms the vase-like shape of a glass sponge. The regular arrangement of the symmetrical spicules makes a glass sponge more symmetrical than most other sponges. The clusters can be highly ornamented with additional branching, creating beautiful skeletal lattices. The arrangement is also functional; it turns out a glass sponge skeleton is 100 times as stiff as an aluminum tube of the same size.