FBI agents in the Boston field office have launched an investigation into the site. They also have served MIT with a grand jury subpoena asking for "any and all subscriber information" about the site, which was initially hosted in a campus dormitory but has since moved to a commercial provider.

MIT said in a letter to bonsaikitten.com's pseudonymous webmaster, a graduate student using the alias Dr. Michael Wong Chang, that it will wait until Sunday to turn over records that would identify him by name.

"I was surprised," Chang said. "I really thought that the FBI had better things to do. That's your tax dollars at work."

Bonsaikitten.com is, of course, a joke devised by prankster MIT students -- who else would talk about "rectilinear kittens?" -- to provoke owners of kittens, an adorably fuzzy topic that's usually beyond parody.

Bonsaikitten.com offers to sell visitors a custom-shaped kitten -- the site says "typical wait time for a fully shaped Bonsai Kitten is 3 to 4 months" -- but the site does not list prices or a mailing address for where to send money orders. It does, however, occasionally receive requests for more information.

It also has sparked tens of thousands of hate-mail messages, anti-Bonsai Kitten groups on Yahoo, and even a blistering denunciation from the venerable Humane Society of the United States.

For the site's fans, watching e-mail nastygrams arrive has become a kind of spectator sport: There's even a mailing list that lets bonsaikitten.com aficionados view any mail sent to the site's webmaster. A typical message: "This site is horrible! You should go in a mental hospital! You son of a bitch! I'll do my best to shut down this site and your disgusting hobby!"

A gun-toting investigator from the Massachusetts Society for the Prevention of Cruelty to Animals reportedly stopped by campus and quizzed MIT network administrators about the intent of the site. Under state law, MSPCA investigators are deputized as "special state police officers" with investigation and arrest abilities.

The combined efforts of animal rights proponents, including such ardent activists as the closed-subscription "meowmies" group, seem to have prompted the FBI to launch its investigation.

"Why are they doing this?" asks Harvey Silverglate, a prominent Boston criminal defense attorney. "I think the answer is that political correctness has infected the FBI."

"The kind of fanatical end of the spectrum animal protection movement has affected them," says Silverglate, a partner at Silverglate and Good. "They want to be the good guys. They massively run rampant over Americans' liberties but they want to be seen as nice fuzzy guys who want to protect kittens."

Silverglate predicts that when the FBI realizes bonsaikitten.com is not serious, the bureau will quietly abandon its investigation.

Ellen Kearns, an FBI agent in the bureau's Lakeville, Massachusetts office who is involved in the investigation, could not be reached for comment.

Nadine Pellegrini, the assistant U.S. Attorney who signed the subpoena, refused to discuss the investigation. "I'm making no comment," Pellegrini said.

The subpoena does not discuss what law the bonsaikitten.com operators allegedly violated. But Pellegrini hinted that it was based on a relatively recent federal statute: "I would assume there's a case, if there's a law, but I'm not making any comment."

In December 1999, President Clinton signed a law that makes it a federal felony to possess "a depiction of animal cruelty" with the intent to distribute across state lines -- such as on the Internet. During a floor debate, Rep. Elton Gallegly (R-Calif.) claimed that "sick criminals are taking advantage of the loopholes in the local law and the lack of federal law on animal cruelty videos."

The law, which observers at the time said probably violated the First Amendment, only applies to images, videos, and sound recordings that are distributed "for commercial gain" -- and bonsaikitten.com's tongue-in-cheek descriptions of mail-order cats in bottles appears to have given the FBI sufficient justification for an investigation.

The national Humane Society, based in Washington, applauded the FBI's efforts.

"If the FBI is looking into this, that's great," said spokeswoman Karen Allanach. "Anything to discourage animal cruelty would be very helpful.

Allanach said she's not sure if the site is a parody -- and even if it isn't, it should be taken offline because it could encourage people to experiment on their own household pets.

"It's totally promoting animal cruelty," Allanach said. "They consider it a sick joke. People will take it seriously. Animal cruelty is not funny. Animal torture is not funny. We would like bonsaikitten.com to be removed permanently."

When asked whether someone has the First Amendment right to advocate for animal cruelty, Allanach replied: "That's a great question. That's at the heart of a lot of debate."

Jered Floyd, a recent MIT graduate, says animal rights activists -- who have successfully pressured hosting services to ban bonsaikitten.com until rotten.com offered it server space -- don't have a sense of humor.

"The First Amendment protects all speech, no matter how offensive some people may find it," Floyd says. "The site is clearly a humorous endeavor. The fact that a number of people seem to have very little sense of humor isn't relevant."

A letter dated Feb. 1 from MIT lawyer Jeff Swope says that federal law requires the university to notify students when it receives subpoenas for information about them. It says that "pursuant to that legal process, MIT will produce such information, no earlier than Feb. 11, 2001."