THE REVIVAL of Don Siegel's 1956 production of "Invasion of the Body Snatchers" at the K-B Fine Arts is doubly welcome. It facilitates comparisons with the fascinating and apparently successful remake by Philip Kaufman that opened at Christmas. It also restores the original picture as closely as possible to Siegel's original conception, which was blunted when executives at Allied Artists insisted on adding a reassuring epilogue -- which then necessitated a stilted prologue and intrusive voice-over narration.

Although hamstrung by these little enhancements and released without fanfare as another horror programmer from a minor studio, the original "Body Snatchers" slowly but steadily acquired an enthusiastic "cult" audience and earned a place of honor in the history of both science-fiction thrillers and lowbudget sleepers.

Indeed, it gave a delightful new meaning to the term "sleeper" by exploiting the premise of dehumanization by an alien life form, instinctively bent on transforming people into emotionless replicas while they slept. The victims went to bed humans but awoke zombies, replaced by doubles that emerged from giant pods and matured overnight. Superficially identical to their prototypes, these doubles were purged of individuality and passion.

While hiding from their transformed friends and neighbors, Dr. Miles Bennell, the protagonist played by Kevin McCarthy, cautions Becky Driscoll, the woman he loves, "We can't close our eyes all night or we might wake up changed."

He is also given an explicit -- and eloquent -- summation of the allegorical theme:

"In my practice I've seen how people have allowed their humanity to drain away, but it happened little by little, not all at once....It's happening to all of us: We harden our hearts, grow callous.... Only when we have to fight to remain human do we realize how precious it is."

In the climactic sequence Miles and Becky, portrayed by Dana Wynter, elude pursuing townspeople, or townspods, by taking refuge in a cave. Hearing the sound of singing nearby, Miles leaves Becky briefly to determine its source. The hope of sanctuary is dashed when he discovers that the music emanates from a truck radio. The truck itself is being loaded with pods from a vast field in which they're under cultivation. Returning to the cave, he discovers Becky apparently hovering on the brink of sleep. He lifts her, begins to carry her away, falls and tries to rouse her with a kiss. To his horror Miles recoils to confront a snatched, implacably hostile Becky.

The literal-mindedness and redundancy of the voice-over narration are never more galling than at this juncture, the film's most wrenching emotional moment. One scarcely needs to be reminded of the hero's loss. Dana Wynter was an exquisitely beautiful young actress in 1956. Moreover, she and McCarthy were an extraordinarily beautiful and appealing couple on screen. The last thing you want to hear is an explanatory line as idiotic as the one you do hear, presumably coerced out of McCarthy, director Siegel, screenwriter Daniel Mainwaring and producer Walter Wanger:

"I didn't know the real meaning of fear until I kissed Becky."

Talk about a kiss of death! Whoever demanded that line deserves to roast over eternal flames of exploding nitrate.

The filmmakers themselves seem to fudge a little detail at the climax. Although we've been led to believe that the pods produce duplicates of their victims, Miles appears to pick up a still human Becky, who becomes inhuman as a result of succumbing only briefly to sleep. The transformation itself was a devastating twist added by the filmmakers. In the literary source, Jack Finney's "The Body Snatchers," first published as a three-part serial in Collier's in 1954 and then expanded into a novel published by Dell a year later, Miles and Becky succeeded in defeating the menace. They made it literally too hot for the pods to remain on Earth.

It's interesting to observe how Kaufman and screenwriter W.D. Richter contrive to exploit and refine elements from both Finney's novel and Siegel's film in the new movie version, an unusually imaginative and adroit but also self-conscious remake, which transposes the setting from a disarmingly serene small town called Santa Mira to a systematically ominous, threatening San Francisco. The climax, for example, fuses the big conflagration envisioned by Finney with the romantic tragedy introduced by Siegel and Mainwaring.

The hero and heroine, now a public health inspector named Matthew Bennell and a lab technician called Elizabeth Driscoll, attractively portrayed by Donald Sutherland and Brooke Adams, wind up at a dockfront warehouse where pods are being cultivated. The new Dr. Bennell behaves downright foolishly when he leaves Elizabeth in the vicinity of this plant to investigate the mysterious sound of "Amazing Grace" being played by bagpipers.

Upon his return he tries to revive the human Elizabeth, who begins to shrivel up and disintegrate in his arms. This astute and visually stunning shock effect takes the metamorphosis of Becky a devastating step further. A naked, dehumanized duplicate of Elizabeth suddenly appears to confront and then pursue the stricken Matthew, who escapes to set the plant ablaze for a spectacular but ultimately futile gesture of heroic defiance.

The source of fear tapped by "Body Snatchers" is so authentic and deep that one can imagine the story being remade effectively every few years. Praising the first "Body Snatchers" in a study of horror films published in 1967, Carols Clarens wrote, "The ultimate horror in science fiction is neither death nor destruction but dehumanization, a state in which emotional life is suspended, in which the individual is deprived of feelings, free will and moral judgment.... This type of fiction hits the most exposed nerve of contemporary society: collective anxieties about the loss of individual identity, subliminal mind-bending, or downright scientific/political brainwashing.... Zombies, like vampires, seemed so incontrovertibly different; the human counterfeits of... 'Body Snatchers' are those we love, our family and friends. The zombies are now among us, and we cannot tell them and the girl next door apart any longer."

Pauline Kael, who recently raved about the Kaufman version, was also an early supporter of the Siegel film. When she ran the old Cinema Guild and Studio theaters in Berkeley, Calif., in the late '50s, Kael frequently booked "Body Snatchers" during exam weeks and promoted it as the ideal movie to see if you wanted to stay awake for the rest of the night.

People inclined to fear or fight off sleep must be particularly susceptible to the premise, which adds an insidious new note of supernatural apprehension to the venerable bedtime prayer for children, Now I lay me down to sleep/I pray the Lord my sol to keep/If I should die before I wake/I pray the Lord my soul to take . In "Body Snatchers" human beings are rendered into soulless copies of themselves by an unholy, insatiable alien microorganism.

The Siegel film was intended to be a crisp, straightforward, uncompromising exercise in terror, beginning with the return of the hero to Santa Mira after a medical convention and ending with his escape to the highway, where he tried to arouse the attention of passing motorists with frenzied, unheeded warnings. The movie was supposed to fade out on close-ups of McCarthy screaming "They're here!" and "You're next!" right at the audience.

Siegel was forced to add a framing device peculiarly reminiscent of the one imposed on "The Cabinet of Dr. Caligari" a generation earlier. A prologue showed a hysterical McCarthy being interrogated by a psychiatrist (Whit Bissell) summoned from the state mental institution by police officers. The doctor agreed to listen to McCarthy's account of what happened in Santa Mira, and the body of the story began with voice-over narration, which returned from time to time but was never an essential storytelling device.

At the end an epilogue was appended in which Bissell was about to dismiss McCarthy's ravings until he overheard policemen mention an accident that confirmed the hero: an overturned truck was found with a cargo of bizarre giant pods. Swinging into action, Bissell commanded, "Call the FBI! Blockade all highways leading out of Santa Mira!"

When distribution rights to the Siegel film were acquired a couple of years ago by Crystal Pictures, a New York company, the new distributor suggested restoring the original conception by making a couple of judicious cuts, i.e., eliminating the prologue and epilogue. Siegel was agreeable, and the cuts were made. Although exhibitors may still order the original padded version if they so desire, Crystal prefers to rent the expurgated version, which in this rare instance happens to be the more genuine article.

Removing those tacked-on sequences accomplishes several desirable or revealing artistic results: the running time of an already incisive thriller is reduced to a super-compact 70 minutes; the voice-over narration becomes unmistakably superfluous; and the responsive shrink played by Bissell disappears, leaving the field exclusively to the treacher-ous shrink played by Larry Gates, who looks more like a cynical cop but exposes his loyalty to the invaders by trying to smoothtalk the defiantly human characters out of their fears.

In the Crystal cut Siegel's movie now ends with McCarthy's face frozen in an agonized, Cassandra-out-of-Edvard Munch close-up. The fadeout of Kaufman's remake was obviously designed to recall this image with a horrifying new twist. Sutherland echoes McCarthy's gaping-mouthed scream of alarm, but the impulse prompting his scream has been ironically, wittily altered. Working in a less restrictive filmmaking climate, Kaufman and Richter were able to follow through on the dramatic logic Siegel and Mainwaring were compelled to violate.

Both versions are likely to achieve enduring popularity and be joined by subsequent versions adding the distinctive stylistic and psychological imprints of other filmmakers working in altered filmmaking climates. When the story is shot again, it might be amusing to portray the heroine seeing the hero transformed before her horrified eyes. It's not often that one can compare the original version of a movie with its remake. As a rule, the company producing the remake acquires the original and takes it out of circulation.

The pleasant novelty of the experience is enhanced in this case by the unusually high quality of each version and by the partial liberation of the original from an old set of expository shackles. The new revival of "Invasion of the Body Snatchers" reaffirms its integrity. This is one of the most effective and satisfying low-budget thrillers ever made, a superlative example of how a quickie, shot in three weeks on a budget of $400,000, can sometimes transcend its limitations and emerge as a classic.