No other sculptor can turn paper, wood, flax and wire into wall sculptures of such intriguing ambiguity as Yuriko Yamaguchi. In the ongoing series of works titled "Metamorphosis," begun in 1991, she conjures those materials into shapes so familiar yet so enigmatic that it's almost impossible to keep from touching them, from physically examining them to try to divine their meaning.

But even if one could handle Yamaguchi's subtle, sensual and earthy new works on display at Numark Gallery, the likely result would be a few answers and many more questions. Such is the evocative power--aesthetically and psychologically--of her sculpture. "Metamorphosis" is an apt metaphor for what has gone on in the series over the years. The sculptures, often consisting of a number of individual pieces grouped together on a wall, have gone through various transformations paralleling an organism's life cycle. Certain forms, taken from nature and the human figure, have recurred since the beginning.

Along the way, however, the beauty, subtlety and layers of meaning have become deeper, denser and more vivid. Some pieces in previous installments had a static quality, as if they were dead butterflies pinned to board. The new works are more vibrant; many appear to be on the verge of movement. All of them look like they might produce weird sounds when the gallery is deserted at night.

But what makes Yamaguchi's work so compelling is its audacious ambiguity. Nothing is quite what it seems, beginning with the physical appearance of the works. With many of the pieces, it's almost impossible to know without referring to Yamaguchi's written description whether a sculpture is animal, vegetable or mineral.

Many of the pieces look as if they were made from rocks taken from a stream bed or the petrified innards of an ancient race of humans. But the kidneys skewered on a stick turn out to be paper, as do many of the rocks. That knowledge is unsettling--many of the works look so heavy that it seems the wall could crumble at any moment. Too add to the confusion, some of them are actually made of metal and quite heavy.

Those kinds of contradictions crop up time and again in this exhibit. Most of the sculptures look ancient, musty and grimy, like objects from an archaeological dig. Yet many of them have an undeniable, gut-level sensuality that transcends history, culture and time. There are curves and clefts and ripples, as well as phallus and breast shapes. Depending on the angle from which the works are viewed, the negative space (the white wall delineated by Yamaguchi's forms) can suggest various parts of the human anatomy.

The artist's style is complex, contradictory and tough to categorize. There are strong strains of minimalism and conceptualism in works like "Metamorphosis #83," which consists of four distinct pieces affixed to the wall. The first looks like a cluster of milkweed pods. The second resembles a cigar on a bed of straw in a cradle, bound with string. Part 3 is a stack of ancient papers skewered on a pair of wooden spikes. The final piece is a board holding what appear to be the wooden handles of six rubber stamps that bear labels: "Randomness," "Hypersensitivity," etc. But a grid pattern, one of the iconographic cornerstones of contemporary abstraction, is also present. And so is a decidedly Japanese lyricism--deceptively simple and hauntingly personal in nature--that makes Yamaguchi's sculptures seem like visual haiku in which the essence of human existence has been distilled into a few elegant shapes.

Yet even the shapes are ambiguous. Is that really a cigar in "Metamorphosis #83?" Could it be a seed pod? A petrified body part? We can't know. Yamaguchi makes it easy to presume that there must be some logical pattern within that group of four works. But in the end, it's up to the viewer to connect the dots any way he chooses. Her sculptures are essentially vessels that you fill with your own meaning. Many artists try to achieve that. Few succeed so well.

Yamaguchi says she will continue with the "Metamorphosis" series until she has created 108 rows of sculpture because 108 is a significant number in Japanese sculpture. At the new year, for example, the bells in temples chime 108 times.

Whether she can sustain the series at this level of complexity, depth and vigor, only time will tell. A smattering of works in the gallery's back room, particularly the small sculptures featuring postcard-size mirrors reflecting newspaper clippings, seemed contrived and listless in comparison. But given what she has done with the series over the past eight years it seems likely that Yamaguchi's evolution will continue.

Yuriko Yamaguchi at Numark Gallery, 406 Seventh St. NW, Tuesday-Saturday, 11 a.m.-6 p.m., 202-628-3810, through Oct. 30.

CAPTION: Yamaguchi's "Metamorphosis #82," at Numark Gallery.