A few additional comments on glass sponges. First, as Tom Watters indicated - but it might be well to state it outright - these are not mollusks. They are members of an entirely different phylum - the Porifera - sponges. The "watering pots" mentioned by Jr in his inquiry, and the glass sponges are both elongate and tubular in shape, and both have a perforated plate covering their upper end. But they are not related at all. Watering pots are bivalve mollusks. Most sponges have tiny needlelike spicules of either calcium or silica embedded in their body wall. The shape and chemistry of these spicules is an important characteristic used in classifying sponges. In the glass sponges, the silica spicules are fused together into a rigid latticework that resembles lace. Some of them are quite beautiful, and they are surprisingly strong considering that they weigh almost nothing. Also, as you might expect, being made of fused silica (essentially natural "fiberglass") they are very chemically resistant, and in spite of their delicate appearance can be safely soaked in bleach or other chemicals to clean them (other kinds of sponges would dissolve or disintegrate). Most glass sponges are deep water species, usually dredged at depths of 800 to 1500 meters, and some have been taken at depths of 3 miles. The story of the commensal shrimp mentioned by Tom is also interesting. An immature male and female shrimp are just the right size to enter the tubular body of the sponge through one of the natural holes in the lacelike skeleton. But, once they mate, spawn and molt, they are too large to get back out through the same holes. So they spend the rest of their lives together in a "glass cage", subsisting on plankton brought in by the feeding currents of the sponge. In old Japan, a glass sponge with the pair of enclosed shrimp was traditionally given as a wedding gift, symbolizing the permanence of marriage. Paul M. Rhode Island