I did not see the first Ace Ventura movie. I had serious reservations about going to see the second one. Rest assured, I do not plan to see the third.

There will be a third Ace Ventura, Pet Detective, just as surely as there will be another magazine article about its star, Jim Carrey. Mr. Carrey is a gross-receipts magnet, and the only name worth mentioning from the second Ventura movie, When Nature Calls. He has long since established his reputation as a star. Now, with his fourth lowest-common-denominator comedy in two years, he has sealed his fate as someone who will never be offered a particularly good serious role.

Such musings probably don't cost Carrey too much sleep, though. He's wildly successful as a comic actor -- if you measure success by box-office draw. Is his performance in When Nature Calls fraught with subtleties and emotional impact? Um ... no. Was he wrong to take a job in a film that represents, even for Carrey, a plunge downward in script quality and general good taste? I guess that depends on how badly he wanted the money.

Not that it matters, but When Nature Calls is a terrible movie. Written and directed by big-screen newcomer Steve Oedekerk, it purports to tell the story of Ace's quest to find Shikaka, the purloined white bat of the Wachati tribe. If he finds the bat in time, the Wachati princess can marry the Wachootoo prince, and everyone will live happily ever after. If not, war is imminent. It's hardly enough of a premise to keep even this gag-a-thon chugging. But it seems petty to take When Nature Calls to task over its plot; it's like faulting a sailboat for having no wheels.

Unfortunately, this film is a little light on jokes, too -- at least on jokes that most of us didn't hear in the third grade. "Spank you. Spank you very much," comes up several times.... There's a bit where Ace confuses the words "peanuts" and "penis".... At one point, Ace says, "Nonsense, poopy-pants," and at another, we see him masturbating in silhouette.... A gorilla rapes the villain.... Find anything funny yet? Carrey supporters will say the joke is in the delivery -- in the facial expressions and the intonation. But even played to the manic hilt, as it is (of course), this dreck is more embarrassing than it is humorous.

There's no denying Carrey's talent; he earns his money. But he needs material. Yes, he makes funny faces, and he does have a knack for delivering a line. But the man can't simply walk on-camera, screw up his face, and say "all righty, then" for two hours, and that's exactly what Oedekerk expects of him.

When he does aim for comic substance, Oedekerk usually takes a cheap shot at African native culture. The film's attitude, like Ace's, is that this is a culture of little consequence -- easily dismissed, and hardly worth fretting over, let alone trying to understand. So we get the bat-shit dinner entrees, and the Wachati custom of hockering in someone's eye to display affection, and the inevitable problems in translation. Savage tribal rituals are always good for a larf, as well. At a certain point, such cavalier cheap shots begin to overshadow the scraps of dialogue that might have worked. It seems as though I must've chuckled a few times. But the occasions don't stand out in memory, and I'm not feeling anywhere near charitable enough to try to recall them.

I hope that Jim Carrey fans will be disappointed in When Nature Calls; they have reason to be. Carrey's gift for physical comedy is without recent peer, and there's nothing shameful in taking a good pratfall -- or in making faces for the camera -- especially if you're good at it.

A movie doesn't have to be Citizen Kane to be worth watching. It doesn't even have to be Modern Times, comparing slapstick to slapstick. But at this point, Carrey has his pick of roles. He must be able to see that Ace Ventura is no Tramp. And he should be able to see that, as Ace Ventura, he's wasting his talents.