In "King Kong," on the night of Kong's big opening on Broadway, a woman in the audience asks her companion what to expect. He tells her it will be "some kind of gorilla" and she snaps, "Gee, ain't we got enough of them in New York?"

It has been the fate of the noble gorilla to be turned by popular culture into either a synonym for boor or a slobbering lustful monster. But "Gorilla," tonight's National Geographic Special on public TV (Channel 26 at 8 p.m.) proves that this private and erudite creature is hardly so low a mammal as once was thought -- in contrast to the Hollywood gorilla of "Kong" and other briefly recalled films in which men dressed as gorillas were occupied chiefly with abducting blonds and delivering haymakers to hunters.

The gorilla, with the chimpanzee, is probably "our closest living relative," says narrator E. G. Marshall. Gorillas share with humans such maladies as arthritis, chicken pox, tuberculosis, the common cold and loneliness when separated from their extended families. Gorillas are "shy and gentle" and live in "remarkably stable family groups." They rarely attack people "unless severely provoked," and it is mournfully estimated by some naturalists that they will be extinct in the wild by the end of this century.

What a piece of work is ape. Exceptional footage captures not only photogenic citizens of the world's declining wild gorillas studied in captivity, including the world-famous Koko, who has been taught the sign language of the deaf by Dr. Francine Patterson near San Francisco. Koko holds a child's Viewmaster up to her eyes and changes the picture with the click lever until she loses interest.

The documentary also looks back to Dr. Dian Fossey's stalking of the wild gorilla in Rwanda, Africa, and the cherished companion she found in Digit, a particularly friendly and handsome giant. But Digit was killed in 1977 by poachers; his head was cut off and mounted and his hands were severed so they could be turned into decorative ashtrays, all of this netting the poachers about $20.

There is something incomparably sad in seeing the remains of Digit being brought to Fossey on a litter. The Mountain Gorilla Project, which grew out of this tragedy, now finances patrols of the area by armed guards in order to prevent such killings.

Perhaps the most impressive footage was shot at Howletts, a 55-acre British estate turned into an animal sanctuary in 1956 by businessman and nature lover John Aspinall. Twenty gorillas -- believes to be the world's largest private collection -- romp and cavort in a large enclosed area not only with each other, but also with Aspinall, who can be seen tumbling and rough-housing with a 350-pound male, among others.

Gorillas appear to be intensely social animals. Taken out of captivity, and away from contact with a large family unit, a mama gorilla may simply forget how to care for a baby. And so one of the few gorillas to be born in captivity, Toni, dies at the age of 18 days at a Columbus, Ohio, zoo, despite the intervention of a human pediatrician.

At a zoo in Basel, Switzerland, Jorg Hess tries experiments designed to alleviate one of the great curses of gorillas isolated in captivity: boredom.

The gorilla cage in strewn with strips of paper, the gorillas are allowed back in, and they are momentarily diverted by their new toy, one of them wrapping himself up in like a Christmas present.

Woe unto parents who don't watch this wonderful, enthralling show with their kids.

Through 15 television seasons, the last six on public TV, the National Geographic Specials have been an uncommonly consistent source of illumination and amazement. Since 1976, when the series moved to PBS, Gulf Oil has invested $25 million in the program. Thus it represents a dual rarity: beneficence by an oil company, and a totally successful project initiated by a Washington-based bureaucracy.

"Gorillas" is a kind of follow-up to the 1976 "Search for the Great Apes," another of the Geographic's outstanding hours. Barbara Jampel -- who wrote, produced and directed "Gorillas" -- has kept it from being a provincial view, in that the study of gorillas is not seen merely as a way of learning more about human beings.

Thus the program ends movingly, beautifully even, with a shot of a little boy reaching out for a young gorilla's hand -- a sort of cosmic grasp worthy of Stanley Kubrick -- while Marshall quotes writer Henry Beston, who wrote of gorillas, "The animal shall not be measured by man. They are not brethren, they are not underlings. They are other nations, caught with ourselves in the net of life and time -- fellow prisoners of the splendor and travail of Earth."