A group of subversives calling themselves the Cantabrigian Hibernation Army pulled off the "bear napping" of the century last weekend when they took a stuffed grizzly from his graduate school dormitory.

The bear's owner, Gary Rosenberg, a graduate student in biology, said yesterday that he returned Sunday from a skiing vacation in Montreal to find Rubenstein, the stuffed bear gone, and a note left in its place. The note said that the bear was being "treated well" and that Rosenberg should "wait for further instructions."

Since Sunday night Rosenberg has received two ransom notes, as well as a message on a friend's telephone recording machine demanding 200 "clams" for the return of the bear.

Rosenberg said that he was to leave the money in a book called The Betravers in Hilles library. "I think the conspirators have a perverse interest in clams as a sort of cult figure," he added.

Instead of depositing the mollusks, Rosenberg left a note in the book Monday demanding proof that the stuffed bear was alive. Tuesday he received four black and white snapshots of Rubenstein blindfolded on that day's New York Times.

After failing to deliver the ransom that night. Rosenberg received telephone threats that "The bear will suffer," he said.

Thursday Rosenberg received two new snapshots, one showing Rubenstein with a plastic bag over his head, gagged and tied to a chair. "I think it's hysterically funny," Rosenberg said.

Rosenberg, a teaching fellow for Biology 7b, said the bear was a regular at his review sessions.

"Meeting the bear has been one of the greatest educational experiences of my Harvard career," said Lewis B. Silverman '86, a fall Bio 7b student.

"I'm just waiting for further instructions." Rosenberg said, adding. "I don't think in the long run they'll harm him."