American Ballet Theatre’s annual spring season at the Metropolitan Opera House, opening tonight with a gala performance, resembles a yearly reunion of intimate but peripatetic members of a guild or club or professional society. Since ABT was founded in 1940, it has functioned to some degree as a confederacy of free agents, highlighting many guest stars and part-time stars. Over the last decade, there seem to have developed two different ranks of principal dancers in the company: those who perform only during the company’s Met seasons and those who appear as well in its fall seasons at City Center and on tour across America. And since ABT does not perform 52 weeks a year, even the dancers who do it all with the company do additional outside work. Take the principal dancers we’ll be watching at the Met over the next two months: Angel Corella is directing his own ballet company in Spain. Gillian Murphy danced “Swan Lake” with the Kirov Ballet in St. Petersburg last March. Ethan Stiefel is now dean of the School of Dance at the North Carolina School of the Arts. Nina Ananiashvili runs the state ballet company in her homeland of Georgia. And Diana Vishneva dances all over the world with different companies, including her native Kirov Ballet.

Over the course of the next two months, ABT will premiere a new ballet by Twyla Tharp and revive Harold Lander’s “Etudes,” which joined ABT’s repertory in 1961. But most of the Met’s repertory consists of full-length narrative ballets, created during the 19th century, the decades during which what is now the core canon for classical ballet companies was established.

This season, coming to the fore in this repertory is ABT principal dancer Herman Cornejo. Mr. Cornejo is short, energetic, and technically prodigious, which could posit him in the “demi-caractère” realm. This season, however, he will move into the “danseur noble” category, taking roles that are aristocratically reserved and sometimes psychologically searching as opposed to overtly enthusiastic. Mr. Cornejo joined ABT in 1999, and the company was probably as correct in its decision to make him wait to do these roles as in its willingness to let him try them now. Casting shouldn’t be static; performers mature and evolve and casting should reflect that. We’re living in a ballet climate in which very young dancers around the world are thrown headfirst into roles they cannot possibly begin to do justice to. Starting these roles after a decade of performance experience is better than starting them too early.

That said, there aren’t enough opportunities for the company’s younger or lower-ranked dancers to advance in the classics. At the Met, the company wants most of its principal dancers to dance in as many full-lengths as they can, which doesn’t give the up-and-coming ones as clear a flight path as they deserve. And the company doesn’t have as many tour weeks as it used to in which to break in dancers in lead roles. Nevertheless, at the Met this season soloist Stella Abrera will make her debut as Giselle, soloist Sarah Lane will dance her first Aurora in “Sleeping Beauty,” and corps de ballet members Cory Stearns and Mikhail Ilyin will make debuts in “Le Corsaire.”

At tonight’s gala, ABT will give a one-time only rendition of Antony Tudor’s “Judgment of Paris.” Tudor, who died in 1987, would have turned 100 this year. Next fall, his works will dominate ABT’s City Center season. “Judgment of Paris” is a corrosive little comedy in which three scantily clad clip-joint hostesses, long past their salad days, entertain a barely conscious customer, ripe for fleecing and impervious to their routines. There is a sense in which “Judgment of Paris” registers as Tudor’s cautionary rebuke to the fit specimens he worked with day in and day out, reminding them that their prowess, too, would inevitably fade. As has happened at ABT galas in the past, the three floozies will be danced by retired ABT dancers: tonight they will be Bonnie Mathis, Kathleen Moore, and Martine van Hamel. Evidently, none is afraid to let her character’s age be a comment on her own. But I can bet, too, that each will enjoy showing us that she’s in shape superior to the dilapidated dame she impersonates. In the acting roles of waiter and patron, we’ll see ABT artistic director Kevin McKenzie and associate artistic director Victor Barbee. All five dancers took on many roles in the Tudor repertory during their ABT careers, and thus tonight’s “Judgment” will provide its own homecoming within the annual reunion that ABT’s Met seasons allow.