A mysterious disease the last several years has almost made Japan's pearl oysters an endangered species. Unless a solution is found soon, Japan's vernerable pearl industry fears it may be on the way out. If the oysters die en masse again this year, "most of us will be forced to quit,"said Toru Nishi, a pearl grower who has been in the business for more than 40 years. "I'm afraid the entire industry will go belly up".