To be adored by the ladies, put on a more natural garb which does not hide your best features."

Julas Leotard, a 19th-century trapeze artist, gave that advice to his circus colleagues in Paris and London. And the snug-fitting cotton and silk dance costume, named for him, became the popular dress for dancers and acrobats.

Since then, the one-piece stretch garment has found a wider audience. The increasing popularity of donce and the growth of the exercise classes have inspired many to seek out the leotard, and to discover is comfort and versatility.

A sharp contrast to the full-blown, oversized clothes that are popular this summer, leotards have become top-sellers in Washington - worn on the street with skirts and pants, for swimming and even for disco dancing. Many women find them both comfortable because they stretch, and cool because they are porous and often cut quite bare.

Louise Beasley, who just moved to Washington from New York, wears Danskins (except on the job, as a salesgirl at Neiman-Marcus, where leotards won't pass the dress code). She always teams them with a long skirt and flat sandals, "just because they are neat and comfortable."

Patricia Millard, assistant to the president of the Center for Community Change, has made leotards-cumskirts her summer uniform. "I don't seem to perspire as much in hot weather when I wear them," says Millard. "They seem to have natural ventilation."

"It allows me the kind of freedom of movement that nothing else does," says actress and model Miki Dee. "It's great. I can wear them on the street and go right into the swimming pool."

Danskin, which makes the versions currently popular, introduced an all-nylon stretch dance leotard in the early 1950s after considerable commercial success with stretch nylon tights. (During June, Hecht's sold an average of 1,000 Danskin per week.) Danskins makes 43 styles in 31 colors in several fabrics. Margot Fonteyn leotards and Rudi Gernreich's designs for Capezio are also sold locally.

This fall Danskin will receive a Coty Award, the fashion industry's top kudo, "for outstanding contribution to body-clothing for exercise and sport."