Toward the end of the Yves Saint Laurent show in Paris last week, with the sound system playing "Put the Blame on Mame, Boys," a model slunk down the runway in a seductive black silk satin dress. It reflected the fact that the film "Gilda," with Rita Hayworth, is having a popular revival in Paris and Saint Laurent had been one of the crowd in line to see it. But it also underscored a popular theme of last week's spring collections: sensuous and glamorous clothes, particularly for evening.

The haute couture collections were once the big trend setters; designers would dispatch a new silhouette, color or hemline as a trial balloon for future collections. Today, most designers save their innovations for the ready-to-wear shows, not only because those customers who can afford couture price tags aren't looking for fashion fireworks, but because the ready-to-wear shows turn out far more press.

This season there were at least 100 more journalists and photographers than usual at the shows. Karl Lagerfeld's first designs for the house of Chanel provoked a good part of the larger turnout, and resulted in a greater effort by other designers to produce strong collections.

The shows didn't produce any great news, but rather a reinforcement of trends that have been developing for the past year or so. Among those trends:

* An emphasis on fitted clothes rather than roomy ones. Shapeliness comes from slim skirts and belted waistlines and hips.

* Hemlines that usually stop just above the knee. Lagerfeld was a rare exception with top-of-the-calf-length skirts for Chanel.

* Black and white continuing as the favorite colors, used alone or in combination.

* Some shoulder padding or sleeve treatment that gives width to the top of the silhouette.

* Big lapels on suits and dresses, and occasionally spotlighted in white in contrast to the rest of the design.

* The coat dress or fitted suit, suggesting a no-frills, serious look for day.

* Unlimited, movie-star glamor for evening.

It is clear that the woman who pays couture prices wants her clothes to look expensive. There are no casual sweaters and skirts to speak of in these collections. The carefully fitted suits are jazzed up with hats and gloves and bedecked with bold necklaces and earrings. Occasionally, the decorations on the clothes are trompe l'oeil, really knitted into or beaded onto the clothes, rather than separate items in themselves. Marc Bohan's white collars on suits for Christian Dior were really not separate collars at all.

The clothes reminded many of the glamor of Hollywood at its peak, and there was no shortage of glitterati, both theatrical and political, in the front row to appreciate them. Among them were Catherine Deneuve, Paloma Picasso, Madame Pompidou, Pat Kennedy Lawford and Jacqueline de Ribes. Guy Laroche even put one of his superstar clients on the runway: He closed his show with a wedding dress worn by Alexandra Mussolini, granddaughter of Benito and niece of Sophia Loren.