Horny skeleton of the elephant's-ear sponge, from the 

 Mediterranean, a fine-textured commercial sponge 

 valued by potters. (Ralph Buchsbaum) 



The family Clionidae has other well-known borers, 

 some of them busy in coral reefs. Most are sulphur 

 yellow, a few green or purple. Some members of the 

 family Suberitidae encrust the snail shells inhabited 

 by various hermit crabs, and certain species are 

 never found except on such shells, growing until they 

 completely enclose the shell. When the shell disap- 

 pears the crab continues to occupy the spiral cavity 

 formed by the sponge, and it is presumed that both 

 members benefit, the sponge by being carried about 

 during its feeding, the crab by protection from preda- 

 tors (Plate 2). 



The redbeard sponge, Microciona, is a bright red 

 colony that grows as a low incrustation or, in deeper 

 waters, as an erect mass of red branches perhaps 6 

 inches high. It is well known from South Carolina to 

 Cape Cod, and has been much used in experiments 

 on the dissociation and reintegration of sponge cells. 

 A different species occurs in European waters. 



The family Spongillidae comprises all of the fresh- 

 water sponges. It consists of about 150 species, of 

 which about 30 are known from ponds, lakes, and 

 slow streams in the United States. Typically, they 

 form inconspicuous matlike incrustations on rocks, 

 logs, sticks, or leaves in the water, but they may also 



be lobed or branched. Most of the species that grow 

 on the upper side of objects are greenish from the 

 algal cells that they contain, but those on the under- 

 sides of rocks or in fairly deep water have no chloro- 

 phyll to mask their lack of color or their drab shades 

 of tan, brown, or gray. Some species are not green 

 even when growing in light. The colonies spread as 

 small, thin patches perhaps an inch or two square, 

 but in the best spots may be more than 1 inch thick 

 and cover 40 square yards. They are most abundant 

 in clear, quiet waters less than six feet deep, but 

 some species tolerate deep water, or running water, 

 or a small amount of pollution. Sexual reproduc- 

 tion occurs during the summer growing season; and 

 in addition, fresh-water sponges characteristically 

 produce asexual bodies, the gemmules, which lie dor- 

 mant all winter and hatch into new sponges in the 

 spring. They are easily seen in the fall as small balls 

 of cells coated with a protective layer of anchor- 

 shaped spicules. No predator is known to feed on 

 fresh-water sponges, but the larvae of Spongilla flies 

 (insects of the family Sisyridae) pierce the sponge 

 cells and suck out their contents. Fresh-water sponges 

 are of no economic importance except when they oc- 

 casionally block water conduits or reservoir drains. 

 The decay of sponges may give water what is known 

 as "swamp taste." An excellent account of American 

 forms may be found in Pennak's Fresh-water In- 

 vertebrates of the United States. 



The horny sponges, the Keratosa, are typically 

 shallow-water forms of tropical or subtropical seas, 

 but some species extend even into polar waters. 

 Though they all lack sharp spicules, the spongin fi- 

 bers are usually impregnated with hard foreign ma- 

 terials, and only a dozen or so species are soft enough 

 for commercial use. 



The best commercial sponges were for centuries 

 brought up by divers from the shores of the Mediter- 

 ranean, so it is not surprising that the earliest uses of 

 sponges known to us were among the ancient Greeks, 

 and that in Greek mythology Glaucus of Anthedon 

 was a sponge diver. In the Odyssey, before a dinner 

 party for Ulysses, the maids were instructed to wipe 

 off the tables with sponges. When Ulysses had fin- 

 ished with his wife's suitors, sponges were used to 

 mop the blood from the floor. While Greek mothers 

 sponged their houses clean and Greek fathers went 

 off' to the wars with sponge padding in their helmets 

 and leg armor, Greek babies were bathed with 

 sponges and pacified with bits of sponge dipped in 

 honey. In Roman times sponges were used also as 

 paintbrushes and were carried by soldiers as a sub- 

 stitute for a drinking cup, so it is understandable that 

 Christ on the cross should have been ofl'ered vinegar 

 in a soaked sponge. Today the sponge in the bath- 

 room is more likely to be a marvel of modern 

 chemistry, because overfishing of sponge grounds, in 



64 



Reef scene at Nassau. Many sea whips in foreground, two sea fans near center, 

 and lobed masses of the coral Montastrea annularis dominating background. 

 (Fritz Goro: Life Magazine) 



