Like a coral polyp or the larva of a clam, the bryozoan starts life as an almost invisibly minute, free-swimming creature, usually less than a thirtieth of an inch long. After a few weeks it settles on some hard surface, usually a stone, and secretes its limestone shell. New individuals rise from the body of the founder of the colony at various angles, depending on the particular design of the tapestry being produced. Each of the buds, after achieving its coat, sends out new buds. This is the weaving process. The outside of the stone coat often is marked with delicate and bizarre designs discernable under a microscope. These designs always are the same for members of a colony and quite similar for an entire species. They make it possible to identify species in geological formations and this eventually may be of considerable importance for oil geologists. After death a colony usually is broken up quickly by wave action. Sea bottom ooze often is filled with the remains. This ooze, over periods of milleniums, becomes compacted into rock. The weaving process may be very rapid. A colony, starting with a single free-swimming larva, may cover as much as 100 sq. feet. Such colonies have been found on a single stone. They often are found on mollusk shells. At present the bryozoans are economically important chiefly as a menace to the oyster industry. Once they have covered an abandoned shell, oystermen believe, no other oyster will make use of it. About their only other importance to man comes from the fact that some fresh-water species may clog water pipes by their rapid growth. Every bryozoan in a colony remains throughout its life a separate animal, shut off from its fellows by a wall of limestone and leading an independent existence. Nevertheless, in the species pattern it assumes, each colony acts as if it were a single organism. Moreover, a phenomenon unique in nature, every individual appears to be two and in some species three animals in one. Each leads its own life and dies its own death at its own time. But all make up a single microscopic whole.