A research group on sea mammals captured a rather odd porpoise on one of its trips.

Its peculiarity was that it had feet. After they had photographed and measured the poor thing, they prepared to set it free. 

"Wait a minute," said one of the researchers, "Wouldn't it be a kindness if our ship's doctor here were to amputate the feet so that it would be like other porpoises?" 

"Not on your life," exclaimed the doctor, "That would be defeating the porpoise."