What was danced and how it was danced amounted to a manifesto last night as the Ballet Nacional de Cuba started its three-week engagement at Kennedy Center. With "Les Sylphides" as the opening wrok, the company proclaimed its tradition. Michel Fokine choreographed this Chopin suite at the beginning of our century and meant it as the evocation of an older epoch, but it is the original model of the contemporary ballet of mood, musically and movement.

For many years it was standard to give "Sylphides" first on the first night of a season, and no doubt Alicia Alonso, the Cuban Ballet's director, was referring to this practice as well as to the academic tradition which Fokine had restated. We don't, however, often see the work performed so slowly now, with an abrupt upward instead of horizonal flow. This was deliberate, and is a conscious stylixation of the way Alonso herself danced at the beginning of her carrier.

Josefina Mendez in the mazurka and in the pass de deux with the ballet's one man, Jose Zamorano, resembles Alonso in looks, and in the simple way she holds her arms down while the neck is high and the chin juts slightly forward. Though a competent dancer, Mendez is not as miraculously light as Alonso had been. Cristina Alvarez delivered a strong, unsentimental Prelude with almost military phrasing. Only the waltz dancer, Rosario Suarez, moved in a current, continuous style.

"Canto Vital" pointed to the Cuban Ballet's Bolshoi connection - choreographer Azari Plisetski. It's a fun piece of athletic exhibitionism for four men - classical Orlando Salgado, supple Lazaro Carreno, tumbling Andres Williams and stalwart Raul Barroso - but its message about the discovery of cooperation by cavemen is a mere excuse for the beefcake and there is no probing of the Mahler music.

Another pas de quatre, Albert Mendez's "Late in the Afternoon," represented the best of modern Cuban choreography. In this miniature of four sisters - willowy Mkrta Plas as the eldest, strong Marta Garcia as the lonely one, precise Ofelia Gonzalez as the vivacious one and solid Maria Elena Llorente as the questing youngest - Mendez captures the intimacy of Ernesto Lecuona's salon music, but also its intimations of the vast world of the emotions. Mendez's "Rara Avis," with its bird movements for three successive ballerinas and tribal gymnastics for the corps of men, is an inconsistent experiment in forging a new type of plotless ballet. The final section, it which Loipa Araujo rode and strode on the backs and hands of the men, was full of mishaps last night.

Alicia Alonso appeared at the end of the evening in Brian MacDonald's "Remembrance" duet with her fine young partner, Jorge Esquivel. She's in amazing dance shape for a grandmother, but only at rare moments did she represent the great ballerina of yore.