The younger generation of what was once New York society has gotten largely out of hand. Its typical proponent is Gloria Vanderbilt di Cicco Stokowski, who in her teens disported herself at bars, heavily made up, one wedgie on the rail and a foot-long cigarette holder between fingers with crimson mandarin nails. To make the picture perfect, her then-beloved mother was drinking with her. Debutantes (who rarely have debuts any more) are largely silk-lined bobby soxers. They wear slacks and sweaters out loud and mingle with tea-dancers and gin-garglers in the more expensive but no more exclusive drop-ins. The musty, crusty Old Guard is dwindling with death and high taxes. The few who have retained their aristocratic bearing go deeper and deeper into seclusion. But even they are smudged with the sins of modernity which penetrate all walls and past all butlers. Not so long ago, one of our dozen foremost real society matrons was committed to an insane asylum. The husband of an equally blue-blooded top-drawer grand dame was beaten to death by her gigolo when he walked in on them. The in-betweeners, neither young nor old, make pitiful pretense of youthfulness, dance until they are lame and find dignity too old-fashioned for words--the kind of words they use. Many women born to social position are horning into politics, not a few radical. It's smart to talk red and the son of the late head of J.P. Morgan & Company is one of the loudest of this contingent. Divorces among the social names are becoming as commonplace as they are in Hollywood. As a backwash of the war, New York was invaded by many rich refugees and stranded titled bums. The latter found doors wide open for them. What is left of Inanity Fair is on view rarely and only in a few spots. Great palaces have been razed or turned into dressmakers' shops or offices. Increased real estate values, hardships with help, murderous income and inheritance taxes and the disinclination of the younger members to follow the old and more gracious ways have made mausoleums of the mansions. When these fortresses of fashion fell, society went underground. A few Knickerbocker clans, from hidden retreats, still resist attempts at intrusion by war profiteers, black marketeers and that mixed miscellany of the gossip columns--Café Society. Contrary to general belief, that is not a new institution, though for generations it was regarded from above in about the same light as a daughter of a good family who had borne twins out of wedlock. It originated toward the end of the golden 90's, and its father was the esoteric Harry Lehr, successor to Ward McAllister, social arbiter supreme, creator of the great Mrs. William Astor's sacred 400.