☞ In the Spongiae, the soft sarcode of the body is usually supported by a skeleton consisting of horny fibers, or of siliceous or calcareous spicules. The common sponges contain larger and smaller cavities and canals, and numerous small ampullae which are lined with ciliated cells capable of taking in solid food. The outer surface usually has minute pores through which water enters, and large openings for its exit. Sponges produce eggs and spermatozoa, and the egg when fertilized undergoes segmentation to form a ciliated embryo.