As passers-by stared quizzically, Jonathan Lefkowitz of Goshen, N.Y., sat inside a metal cage on the sidewalk outside Harvard Yard, with a pad of paper resting on his lap and a spark of anger in his eyes. A sign on the cage announced he would remain silent for 100 hours.

He and three other animal rights activists are kicking off a week of protest against Harvard and MIT animal researchers by spending the rest of the week cooped in their cages at a very public intersection in the Square.

The activists are a small part of a much larger group of protestors, organized by Animal Defense League Boston (ADLB), who have pressured both universities for months to change their policy on using primates for medical and experimental psychology testing.

"I am sitting in this cage in protest of the 1,500 primates that are experimented on at Harvard," Lefkowitz wrote to reporters on a pad of paper.

Lefkowitz and the other protestors allege that the primates are restrained unnecessarily, that they are deprived of food and water, infected with diseases and "are left in there own feces."

But Harvard officials and scientists have repeatedly denied these claims, saying the animals are treated ethically.

At 6 p.m. last night, the four caged protestors were joined a chanting crowd of at least 50, kicking off a week of demonstrations.

Those protestors began the evening at MIT, marching down Mass. Ave to Harvard Square.

Accompanying the first marchers was a giant banner, approximately 15 feet tall, that declared, "Harvard Tortures 1,500 Primates."

Many of the other marchers carried photographs of primates who appeared contorted, trapped in various metal contraptions. Several animals appeared to be prodded by metal objects. Organizers claimed that the photographs were given to them by a lab technician at MIT, though they did not provide any further documentation.

"World Week for Animals in Laboratories" will culminate on Sunday with a protest at the site of Harvard animal experiments in Southborough, about 30 miles from Cambridge.

ADLB began its push against Harvard-run labs on March 18, with a large Square rally that, according to organizers, attracted about 125 activists.

Both the lab in William James Hall and Harvard's New England Regional Primate Research Center (NERPRC) in Southborough have been vocally criticized by animal rights protestors for years.

"The NERPRC is causing great controversy in the Northeast... Vivisection labs are making billions and billions off torturing animals in the name of science," said protester Danielle M. Tessier, a Northeastern University senior.

"It's actually scientific fraud," she said.

Representatives from the lab have told The Crimson in the past that the criticisms have no validity and that their animal experiments are subject to strict protocols and oversight.

The protests last night drew students and older activists from all over the Boston area, and even a few from Ohio and Chicago. Noticeably absent were Harvard students.

According to event organizers, they sent e-mail messages to Harvard's activist community but did not feel they had to recruit them specifically.

"We've come here as outsiders, but we're really not," Tessier said. "Harvard isn't paying for these experiments, the taxpayers are. And that is everybody."