THE LOOKALIKES

What is the difference between a gull and a tern? a crocodile and an alligator? a seal and a sea lion? The frequency of such questions from visitors to the Bronx Zoo prompted this survey, by a former staff member, of 29 pairs of animals. It's doubtful, though, that many visitors old enough to read these answers would ask about the difference between frogs and toads, caterpillars and worms, or monkeys and apes. A more selective treatment of the lookalike idea would make a satisfactory nature magazine article; here the half-page description of each animal is not diverting enough (references to ""hobgoblins"" and ""Never-Never-Land"" notwithstanding) for the idly curious or substantial enough for the serious naturalist.