The fresh geese Mort Berenson sells at Boston's Quincy Market are perfectly legal. But what about the chicken feet and unhatched chicken eggs he has available for purchase?

It's really better to let Berenson explain himself. He says there is no U.S. Department of Agriculture regulation against selling chicken feet (the part of the chicken without which Jewish cooks over the age of 40 feel chicken soup cannot quite measure up), it's just that USDA specificiations for chicken feet are so stringent, it's more economical to grind them up for fertilizer.

For chicken feet to pass USDA inspection, according to Berenson, "The nails have to be clipped and the feet have to be cleaned in boiling water either three or five minutes. After that they can be looked at and then passed for inspection. To put a man on a production line to do that would increase the cost on them and make it undesireable. Nobody does it."

According to USDA, Berenson is partly right. The nails must be clipped, the feet scaled, but there is no requirement for boiling a particular length of time.

So how does Berenson manage to sell chicken feet?

"I back-door them. I literally steal them or have someone steal them for me," Berenson says with a shrug.

Asked if the government wouldn't come after him if this information got around, he said, "They can come and warn me." What the government has to do is find the source of supply.

How does this "black market" in chicken feet work?

"A guy calls up and says I got 100 pounds of chicken feet for you. Send over $30." Then Berenson clips the nails, per USDA requiremets. "I send a lot of feet to restaurants to put in their stock. The people who buy them remember chicken soup with chicken feet." They are into nostalgia. "Most," Berenson says delicately, "are in their middle years." Berenson sends chicken feet as far away as Florida. They cost $1 a pound.

"Everything is labor," is how he explains the markup. "You have to pay thieves, too!"

Losses, too. Once his truck with boxes of chicken feet was left unattended outside the market for a few moments. By the time Berenson got back to it, the boxes of chicken feet had been stolen. "Can you image how surprised the thief must have been," he said with a grin.

Unhatched chicken eggs dyelah are another "illegal" speciality item at Berenson's stand. Berenson explains: "They cannot be sold by a processor to anyone except someone who will process them further."

According to USDA the immature eggs that have no shell and no white only yolk, can be sold only to a plant that will break them, mix, pasteurize and then freeze them. These frozen "ova", as the government calls them, can then be sold to bakeries for breads and pastries, as well as other food manufacturers. They cannot be sold at retail. "It's illegal," a USDA official confirmed Berenson says, "The government is afraid someone will eat them raw."

To those same "middle years" people, ayelah were the treat in the chicken soup for young children who behaved. Before chickens were so completely processed, it was possible to find them in the chicken cavity along ith the gizzard and liver.

"How can I sell them? I don't buy them any place. I just acquire them," Berenson says, that wide-eyed look of innocence betrayed by the smile on his lips. "I acquire them from secret sources." Berenson says he isn't worried about anyone getting sick. "I know what my customers are doing with them. Putting them in soup. 90 percent of them are purchased by people of Jewish ancestry."

In the past two years he has sold 5,000 pounds, shipping them frozen to Miami, New York, even Georgetown.

Berenson doesn't know if this story is true, but he likes to tell it.

"A caterer in New York was taken to court by USDA% FOR SERVING AYELAH ON THE GROUNDS THAT HE WAS VIOLATING A GOVERNMENT REGULATION THAT DECREED UNHATCHED CHICKEN EGGS TO BE UNFIT FOR HUMAN CONSUMPTION. THE CATERER KEPT ASKING FOR A POSTPONEMENT UNTIL THE CASE COULD COME BEFORE A JEWISH JUDGE. THEN HE BROUGHT A THERMOS OF CHICKEN SOUP WITH AYELAH INTO THE COURTROOM AND GAVE IT TO THE JUDGE. ONE TASTE OF THE CHICKEN SOUP AND THE JUDGE DECIDED THAT IF THE CHICKEN EGGS JUST STAYED WITH THE CHICKEN IN A LITTLE SACK UNTIL IT WAS INSPECTED, THEN THEY COULD BE SOLD."