An inquisitive nine-year-old from Marblehead stumped the experts of the University Museum of Comparative Zoology last week with a query, "Can mules sit down?"

The youngster's moth first consulted the Encyclopedia Britannica, and then turned to the New England Museum of Natural History, who suggested the University Museum.

Used to answering simple questions on vertebrate paleontology and morphology, the Museum was floored by the request. It unashamedly admitted, "We have no authoritative information on mules' sitting down. Why don't you try Ringling Brothers? And if you get an answer . . . we would like it for our files."

"The Greatest Show On Earth" scratched its big top Monday and came up with a reply: "Of course a mule can sit on its buttocks-or 'bottom'."