The glass sponge is a type of deep sea sponge that has the appearance of spun glass. These fragile sponges of the class Hexactinellida are tubular or cuplike in form and have six-rayed spicules which may be solitary or united to form a skeleton. The cloacal cavity is large; the flagellated chambers spindle-shaped. Among the better known glass sponges are Venus's-flower basket, Euplectella, and the glass-rope sponge, Hyalonema, which is firmly anchored by a tuft of long glasslike spicules.
