The Romans, away back in the days of Horace, raised oysters in ponds along the Italian coast, and Eastern nations preserved the custom during the middle ages, when Europe was doing little except quarreling and making pretty pictures on parchment. More recently the French of the Channel coast took it up, and the English followed, finding that their natural oyster and mussel beds were becoming exhausted. The same fate has overtaken our oyster-beds everywhere north of the Chesapeake, and largely there; so that now nearly all the oysters brought to market are those which have been raised upon private planted beds, which men own or lease and attend to as they do to estates on shore; indeed, it is common to speak of such under-water estates as “farms.” [Illustration: SEA-SHELLS IN THE SURF.] An oyster-farm may be conducted in two ways. One is to place upon a certain space of bottom, in some shallow bay, as many young oysters as it will conveniently hold. These young oysters, generally hardly bigger than your thumb-nail, are dredged in summer from certain reefs in deep water, where the oysters are never allowed to grow to full size; and to a large extent they are brought northward by the ship-load from Maryland and Virginia, which have more “seed,” as it is called, than they need for their own planting. These young oysters, protected from harm, and having plenty of space to grow, come to a proper size for market in about three years, and are then gathered by their owners and sold. Another method is to spread old shells, pebbles, etc., on the bottom, to which the floating eggs emitted by adult oysters in the neighborhood adhere. The thick “catch” of infant mollusks hatched from these captive eggs is then taken up and respread in a more scattered way upon new ground, and is allowed to grow to maturity. The oysters raised by either of these methods are of better appearance and taste, as a rule, than those that grow naturally, because each has room enough to perfect its proportions. [Illustration: MELEAGRINA. _Meleagrina (Avicula) margaritifera._ _b._ byssal foramen or notch; _g._ suspensors of the gills.] Mussels, clams of many varieties, and even sponges and peak-shells, are also cultivated to some extent, each according to the plan its natural habits make advisable. In this way certain great areas of favorable ocean-bottom have become as valuable as the neighboring shore-land, or even far more so, if you compare, acre for acre, the yield of the crops below with those above the water-line. But mollusks are useful in many other ways than as human food. As they are known to be the principal food of several valuable fishes, enormous quantities are devoted to baiting hooks in both hand-lining and trawling for cod and similar commercial species. The quaint squids are mollusks, and these are especially useful for bait in certain places and seasons, and are taken in the North Atlantic in vast numbers for that purpose.