Prime primate entertainment: Mrs. Mundis shows that raising a chimp in a New York apartment involves more than 15 pounds of bananas a week. It means reluctant sitters, shredded Pampers, and a cage bolted to the dining room wall. Boris, a little ""fluff bail,"" came from a pet store and stayed for more than a year while the Mundis family doted and coped. They nursed him through pneumonia, taught him to walk on grass, and endured his phases--water play, swinging, spitting, nudism-natural in the wild but not in the living room. Now living in a Chester, England zoo Boris has the best of both worlds (good care, few restraints) and an even larger audience. No, they wouldn't do it again--they had to thwart his natural impulses; here you can share the sentiment and hairy humor without sacrificing a roomful of furniture.