No-legs lay on one-leg, two-legs sat near on three-legs, four-legs got some. It was not really the right time for this riddle, but Bilbo was in a hurry. Gollum might have had some trouble guessing it, if he had asked it at another time. As it was, talking of fish, “no-legs” was not so very difficult, and after that the rest was easy. “Fish on a little table, man at table sitting on a stool, the cat has the bones” that of course is the answer, and Gollum soon gave it.