They say that oysters are an aphrodisiac. By "they", I mean writers from Juvenal, who listed the consumption of "giant oysters" among the habits of lascivious women, to Camille Paglia, who likened the sensation of oyster-eating to that of a certain intimate act. Cassanova is said to have consumed fifty oysters a day. There is some science suggesting that the high zinc levels in oysters stimulate production of hormones like testosterone and progesterone, and have beneficial effects on the metabolism. Other nutrients and minerals in oysters, such as glycogen, B-vitamins, iron, and iodine, are said to promote blood oxygenation, muscle contraction, and stamina. There are those who suggest that the aphrodisiac qualities of oysters are psychophysiological: oysters may enhance the libido for no other reason than that they are expected to. And there have been intimations that the flesh of the oyster itself resembles a particular region of the female anatomy... but I don't really see it.

Of course Valentine's Day dinner must begin with a dozen oysters on the half-shell -- if for no other reason than to set up a sensual bulwark against the torrents of flesh-numbing alcohol that are sure to follow. Above is an image of the mighty midget of the Pacific, the Kumamoto oyster. Kumamoto is a city on the southern Japanese island of Kyushu, relatively close to the now-infamous city of Nagasaki. Its oysters were once unique in the Pacific, indigenous to the warm waters of the local bay. In the first half of this century the Kumamoto was an also-ran to both the Crassostrea gigas species that dominates the cold-water coastlines of northern Japan and the petite Olympia oysters native to the west coast of North America. As Olympia stocks diminished in both supply and popularity, oyster beds from British Columbia to California began importing seed oysters from Japan -- but not Kumamotos, which continued to be a local oddity relished mainly in nearby Kagoshima.

Oyster importation shut down during the Second World War, until General Macarthur's occupation authority jumpstarted the post-war reconstruction of the industry with an order of 80,000 boxes of seed oysters bound for the United States. The supply of oysters from the North had been interrupted (to use a euphemism) by the recent decimation of the labor force in Hiroshima, and so seed oysters from Kumamoto were used to make up the shortfall. Not long thereafter, the Kumamoto oyster died out of its native habitat in Japan due to a combination of commercial impatience (they take a long time to grow to edible sizes in warm water) and pollution. It seems the American armed forces accidentally rescued this rare Japanese oyster just in the nick of time -- by intentionally killing a few hundred thousand Japanese civilians.

This cruel irony turned out to be a boon to the oyster-loving world. Today, all Kumamotos come from the west coast of North America. They have taken root in waters from Vancouver to Eureka. They are sometimes marketed under their less exotic brand name of "Western Gem"; the rococo fluting of their deep-cupped, silver-dollar-sized shells easily distinguishes them from the broad, flat striations of the larger east coast oyster (more on that below).

Kumamotos are small by American standards, but the rampant supersizing of American cuisine has thankfully overlooked the world of fruits de mer. Round and firm, sweet and mild, and too small to inspire revulsion or fear, they are a perfect introduction to the intimidating world of raw oysters. They lack the briny rush of other bivalves, and their metallic mineral flavor is so subtle that you could miss it if you weren't looking for it: Kumamotos are like a fleshy nugget of San Pellegrino. This oyster is all about texture, and its texture is supple and provocative.

The subtle harmony of the Kumamoto is a marked contrast to the stark contradictions of the Blue Point oyster, the other of the two varieties I chose for Valentine's Day.

Named for a town on the Great South Bay of Long Island, Blue Points were the prize of the American oyster harvest for nearly a century. Queen Victoria preferred them above all other varieties; for a time the fishermen of the south shore shipped over a hundred thousand barrels of the shucked treasures every year. The reputation of these magnificent shellfish spread so wide that counterfeiting and theft took hold; the state legislature had to impose one of its first and only origin control appelations on them, and rampant poaching led native fishermen to attempt secession. As with the Kumamoto, the Blue Point oyster has deserted its namesake locality. Encroachment of tidal waters in the first half of the twentieth century raised the salinity of the Great South Bay to the point that its oysters could neither grow healthily nor avoid salt-water predators. Today, the term "Blue Point Oyster" can be used for any east coast oyster of the species once found at Blue Point, but is often used to denote a Long Island oyster.

The wispy filaments of a Blue Point oyster lack the substance of the Kumamoto, but they are suspended in a liquor of potent steely salinity. The Blue Point is a briny bivalve, but it has gossamer flesh; you do not eat a Blue Point as much as you drink it, as you would a gulp of icy seawater. With a squirt of lemon juice -- and if you are so inclined, a dash of tabasco -- the act of swallowing a whole Blue Point oyster may be the epitome of the raw shellfish experience.

There are tricks to preparing and eating oysters, some of which are the stuff of folklore. One old wives' tale holds that you should never eat oysters in months whose name does not contain an "R". There is wisdom in this: oysters begin spawning in May, which reduces their glycogen levels and tends to make them mushy and thin for several months; the warm water and air temperatures of summer can also promote bacterial growth in the beds or in transport. A fear of food poisoning from oysters may also be justified: hell hath no fury like a rotten bivalve in your GI tract, and they spoil easily. To be safe, eat only oysters whose liquor is clear (not cloudy), and only those whose aroma is clean, like that of mineral water or iodine. A fishy smell is a huge red flag; when in doubt, throw it out.

Your safest play is to buy fresh oysters, keep them on ice (without allowing them to become submerged in liquid water) until ready to eat, and shuck them yourself. Oysters should be tightly closed when fresh; the point of an oyster knife strategically directed with some force into the hinge of the shell should wedge it open. Once the hinge is breached, use the edge of the knife to scrape the adductor muscles off of the top and bottom shells. Work over a bowl and be careful not to spill any of the liquor when performing this maneuver; the briny elixir is the essence of the raw oyster. To reduce the risk of gouging your non-knife-wielding hand, you may opt for a kevlar- or steel-mesh glove, or in its absence, a hardy dishtowel that you will not mourn when it is encrusted with the gritty sludge of a dozen oyster shells. You can -- and should -- reduce the mess by scrubbing the oysters under cold running water before shucking, with a wire brush if you've got one.

Traditional accompaniments for raw oysters on the half-shell include lemon juice, horseradish, mignonette sauce (a melange of wine vinegar, minced shallots, and white pepper), or cocktail sauce (an American abomination that masks the oysters' true flavor). The classic service of raw oysters is on a bed of crushed ice and rock salt, and chilled seaweed if the latter is available, but I have always found it most satisfying to drain the little beasts from their shells seconds after shucking, while they still quiver in my kevlar-sheathed hand.

I offered Lisa a dozen raw oysters this Valentine's Day, as I had offered her her first raw oyster a year earlier. Humor me though she did, she apologetically admitted that she was not terribly fond of them. I am crestfallen. The Kumamoto has deserted Japan; Blue Point, New York is bereft of bivalves; and now my Valentine is impervious to the lures of the world's most famous aphrodisiac. There is nothing to be done; the judgment of history crumbles under the weight of my girlfriend's tastes. In the words of James Thurber, the oyster is a blob of glup, but a woman is a woman.