Igor Youskevitch took up dancing at the age of twenty-four and, within a decade, has become the foremost classical ballet artist in this country. His double pirouettes in the Pas de Deux from The Nutcracker were so brilliant and perfect that he appeared suspended above the stage. And his control and grace in slower movements compare only with Andre Eglevsky of City Center.

His partner in this selection, Alicia Markova, is a lyrical performer. Although she chose a less exacting and less exciting variation, The Sugar Plum Fairy, her technique was flawless. To Les Sylphides, she brought more spirit and charm; Michel Fokine's choreography includes a series of tours en l'air which Markova handled beautifully. At one point, however, she tangled with Paula Lloyd who is a more angular, energetic dancer, and who is not particularly well suited to this genre of ballet.

John Krizna's sharpness made the Mazurka one of the evening's high-points. Usually a fine virtuoso, Krizna is too flashy to be a good supporting partner. Yet his Drummer divertissement in the Graduation Ball was a disappointment--probably because he had to twirl drum sticks as well as execute some complicated steps. The ballet itself was unusually gay and frivolous due to the excellence of the cast. Throughout the entire performance, they projected themselves well and always danced as a group.

Les Demoiselles de la Nuit, a premiere for Boston, was the most enjoyable selection of the program. From the humorous antics of cats to the tragedy of a human-feline love, Roland Petit's ballet is both original and dramatic. Tall and tensile Mary Ellen Moylan conveyed the struggle of her love, arching and pawing with convincing quickness and grace. Her costume, as well as those of the ensemble, and the scenery contributed to the frenzied effect.

One balks from praising too much, but Ballet Theatre boasts several excellent principals and a smooth functioning cast. Excepting a few rough spots, one cannot ask for much more.