Last year my friend Alec, who knows me to be obsessive when it comes to candy, asked if I'd tried the new dark chocolate Kit Kat. I hadn't even heard of this bar, but I quickly set out to find one, which meant visiting every single Mobil station in the greater Boston area, because this is where Alec found his.

In the end, Alec brought me a bar, purchased from an obscure pharmacy. It was absolutely mind-blowing, about 23 times as good as the original version. The dark chocolate coating lends the fine angles of the bar a dignified sheen and exudes a puddinglike creaminess, as well as coffee overtones. This more intense flavor provides a counterpoint to the slightly oversweet wafer and filling.

Hershey's introduced the Kit Kat Dark -- along with a rather unfortunate White Chocolate Kit Kat -- in fall 2001, but only as a limited edition. Sure enough, soon after its introduction, the bar disappeared altogether, and I was left in a state of angry bereavement. It was not the first time.

As a kid, back in the '70s, I'd mourned several bars: The Marathon, a simple rope of caramel covered in chocolate, which came in a bright red wrapper that included a ruler on the back, a ruler that was commonly used by those of us with male self-esteem issues. The Choco-Lite, whose tiny air pockets provided a piquant crunch, the oral analogue to stomping on bubble wrap. And, most persistently, the Caravelle, which combined chocolate, caramel, and crisped rice.

I realize these are the same ingredients as in the 100 Grand bar. But I can assure you the two shouldn't be compared. The 100 Grand always leaves me with a mouthful of rubbery caramel. The Cara-velle tasted more like a pastry: The chocolate was thicker, darker, full-bodied, and the crisped rice had a malty flavor and what I want to call structural integrity; the caramel was that rarest variety, dark and lustrous and supple, with hints of fudge. More so, there was a sense of the piece yielding to the mouth. By which I mean, one had to work the teeth through the sturdy chocolate shell, which gave way with a distinct, moist snap, through the crisped rice (thus releasing a second, grainy bouquet), and only then into the soft caramel core. Oh, that inimitable combination of textures! That symphony of flavors!

Around the time I was starting high school, the Caravelle mysteriously disappeared from the racks, which meant that I spent countless hours describing it to one or another bemused shopkeeper, girlfriend, therapist. I was frantic, inconsolable, really annoying.

The disappearance of all these delicacies caused me to start asking a larger question: How is it that candy bars go extinct? The basic answer here is late-model capitalism. Big guys buy out little guys, or drive them out of business, and their candy bars go the way of the dodo. Caravelle's disappearance, for example, dates back to the acquisition of Peter Paul by Cadbury in 1988.