There were still new performances to see on ABT's final spring weekend at Kennedy Center. With casting that featured several pairs of "twins with a difference," one could wonder how much nature, nurture or miracle have to do with the way in which an artist dances.

Susan Jaffe and Lisa de Ribere are both long-limbed, full-bodied young women. Yet, together in MacMillan's "Concerto," Jaffe moved voluptuously as if her body were one long sigh while Ribere's carriage was so high and her impulse so vividly angled that she seemed to be suspended from strings. Did the difference depend on role? Jaffe danced the wistful adagio with Michael Owen; Ribere was defiantly alone. Type casting, though, might have influenced their assignments, with Balanchine's school of anatomic dissection having imprinted Ribere's style and the milder manner of Maryland Youth Ballet having affected Jaffe's. In Ashton's "Rendezvous" yesterday afternoon, Ribere's smart articulation was refreshing against Robert La Fosse's American openness and the tightly reigned high style of "siblings" Warren Conover and Johan Renvall.

Short, fine-boned Marianna Tcherkassky and Elaine Kudo, in Tetley's "Voluntaries" were another instance of "likeness but . . ." Crucial details of shape and style make Tcherkassky's dancing an example of carefully punctuated classicism, even in body-massage choreography. (Magali Messac, in the same role, had a stark power that did much to justify the ways of Tetley to mortal critics.) In both casts, Kudo's fluent plastique suited the ballet to excess. Her quality was used with restraint by a Taylor "Airs" in which she and her colleagues caught the work's frolic, solemnity and muscle spans.

As the sailors in "Fancy Free," George de la Pena, Kevin McKenzie and Brian Adams were winning Saturday night, but not quite in the afternoon. Cynthia Harvey's hard-boiled New Yorker was so mean at the matinee that one wondered why the sailors were in pursuit. At the later performance, she added allure. De la Pena, in the "Fille" duo, had expansive ease but muted the fine footwork that sent his partner, Cheryl Yeager, prancing proudly. Peter Fonseca, as Green Skater in Ashton's "Patineurs," did daring turns, sharp beats, lost his balance briefly but recovered in stride. Unusual for this role was his sensual buoyancy.