The mating of Chi Chi, the London Zoo panda, and An An, of Moscow, has been called off for the time being. Dr Oliver Graham-Jones, London ZooÕs senior veterinary officer, reported from Moscow yesterday that after Chi Chi and An An were put in the same paddock yesterday they Òshowed signs of aggressiveness and were immediately parted.Ó A London Zoo spokesman said: ÒYou canÕt organise Mother Nature, much as one would like to. Naturally we are disappointed, but one must never rush things in the animal world. You canÕt organise a situation like Ôboy meets girlÕ and Ôlove at first sight.ÕÓ The spokesman said that so far as he knew the pandas did not injure each other. Negotiations are now proceeding with officials of the Moscow Zoo to see if it will be possible for Chi Chi to stay in Moscow until later in the year. An autumn wedding was contemplated.