_Director United States Biological Station, Fairport, Iowa._ PRESENT CONDITIONS. THE MUSSEL INDUSTRY. The history of the fresh-water mussel industry gives illustration of the promptness with which an American industry may be developed once the pathway is found. Undertaken in a small way scarcely more than a score of years ago, the manufacture of pearl buttons began almost immediately to assume the proportions of an important national industry. As early as 1898, when the enterprise was only 6 years old, there were about 50 factories in more than a dozen towns along the Mississippi. With improved machinery and methods further expansion occurred, until within a few years the output approximated 30 million gross of buttons, with a value of many millions of dollars. The growth of the industry has continued to the present time, but exact figures will not be available until the Bureau has completed a statistical survey now in progress. Not less important has been a resultant economic change, or modification of custom, that has affected practically every person in the country. Where marine pearl was in rare use, fresh-water pearl, with its quality and price, came to fill a universal requirement. In one decade pearl buttons were high in price, used only upon the better clothing, and commonly saved when clothing was discarded, while in the most general use were buttons of metal or agate or wood, which rusted or broke or warped. In the next decade good pearl buttons, neat and durable, were available to everybody and used upon the widest variety of clothing. A former luxury had become a common necessity. Coincident with the rise of the manufacturing industry, there developed an important and widespread fishery, directly employing thousands of persons and indirectly affecting persons and communities of varied occupation. Commencing on the Mississippi River, the fishery gradually spread from stream to stream, passing from depleted territory to new and rich fields, until it embraced practically the entire Mississippi Basin and a portion of the Great Lakes drainage, from Minnesota to Louisiana, north and south, and from Ohio, West Virginia, and Tennessee on the east to Arkansas, Kansas, and South Dakota on the west. DEPLETION OF THE RESOURCES.