A whole week of "CBS: On The Air" has settled one thing, anyway, Walter Cronkite and Captain Kangaroo are not the same person after all. They were finally seen and photographed in the same room at the same time by CBS.

Of course, we all know that PHOTOGRAPHS can be DOCTORED so you'd never know the difference.

By now, people who have seen the first six shows in the network's 9 1/2-hour 50th anniversary celebration are probably resigned to tuning in the 2 1/2-hour finale, tonight at 8:30 on Channel 9. Coming this far and skipping the conclusion would be like walking out on "Gone With the Wind" just as Bonnie Blue Butler falls off her horse.

May be CBS should have called this thing "Gone with the Air," because almost all its best moments have been excerpts from TV shows long extinct.

So one endures the precious and perky new production numbers for such zany and invaluabel treasures as tonight's reprise of "Surprise Wedding," a riotous parody of TV greed shows from an old U.S. Steel Hour. It stars Sid Caesar, Audrey Meadows and Jose Ferrer.

Preston Sturges himself couldn't have created a more sardonic assault on TV's appeals to cupidity, voyeurism and invasion of the privacy of others than this satire of "This Is Your Life," "Bride and Groom," "People Are Funny" and other such exhibitionisms. "Please," begs Caesar to Ferrer, the gallingly grinny host," "we're not monkeys in a zoo." Often, however, in the course of amusing a nation, television has become a zoo and the men and women in it merely monkeys.

Other highlights tonight include a tribute to CBS Westerns, scenes from the first and last editions of "The Mary Tyler Moore Show," a Perry Mason medley, unjustly short shrift for Jackie Gleason, and Father Cronkite's rendition of a guaintly florid poem, "Network at 50," by Norman Corwin. The program is also marked disorganization, self-aggrandizement and baffingly shoddy editorial judgment.

Before the show ends tonight and 122 stars have been trotted out for a mass bye-bye, CBS Board Chairman William S. Paley, 77, and very rich, appears for a benefiction in which he declares, "America believes us, depends on us, votes us into their living rooms by the tens of millions" and so on.

One expects him to break into song, the way one expected Cronkite to join Moore in a duet on opening night, a moon or two ago.

"CBS: On The Air" has tried to tell us that TV's best is yet to come, but the richness and daring in some of those faded old clips casts some doubt on this and makes wisdom of Archie Bunker's lament. "The world was better when it was the same."